# Hot Math Posts

### How To: Factor a trinomial with negative leading coefficient

In this video the instructor shows how to factor a trinomial with negative leading coefficient. Most of the students are confused when they have to factor a trinomial with a negative leading coefficient. But there are many ways to solve these kind of problems as shown in this video. One way you can do is that take out the greatest common factor (GCF) of -1 from the equation. So pulling the -1 gives you the original trinomial with all the signs of the terms changed. Now go on and factor the ne...

### How To: Evaluate combinations of functions from graphs

YouTube user NotesCollegeAlgebra teaches you how to evaluate combinations of functions from graphs. You start off with a graph and some functions. (f+g)(-3), (g/f)(0) and (fg)(-6). You start looking at the graph and the first line and you get (f+g)(-3)=f(-3)+g(-3)=3+1=4. (g/f)(0)=g(0)/f(0)=2/-3=-2/3. (fg)(-6)=f(-6)g(-6)=(-3). But then when you want to find out g(-6) you realize -6 is not in g's domain. So the answer to the last equation is that it doesn't exist.

### How To: Solve equations with the order of operations

In mathematics, the order of operations define the priority in which complex equations are solved. The top priority is your parenthesis, then exponents, followed by multiplication and division, and finally addition and subtraction (PEMDAS). This video tutorial demonstrates the order of operation with various examples and explains the associated methodology. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autod...

### Find the discriminant (DELTA): quadratic equation

The discriminate of any equation in any degree plays an important role in determining the roots of that equation.

### How To: Simplify fourth roots

In this video the instructor shows how to find out the fourth roots of a number. The properties of fourth root says that for any positive number of a, its fourth roots are real. And for any negative value a, its fourth roots are not real. So split the number inside the fourth root as the product of two perfect squares and then cancel out the power with the fourth root giving its roots. As the fourth roots of a positive number are real, the answer you get is correct. But you cannot find out th...

### How To: Calculate the acceleration of a car on inclined plane

In this video tutorial the instructor shows how to calculate the acceleration of a car on an inclined plane. He goes on to solve a problem he came across which is based on the acceleration of a car on an inclined plane. He shows how to solve this problem by showing how to extract the data from the question and draws a diagram to get a clear understanding of the problem. Now he marks the forces acting on the vehicle and goes on to specify his axes and how to split the components of force along...

### How To: Simplify a quadratic formula result

In this video the tutor shows how to simplify a quadratic formula result. You can solve a quadratic equation using the quadratic formula. The first thing you have to do when given the quadratic equation is bring all the terms to one side so that you have a zero on the other side of the equals to sign. Now the formula to calculate the roots of the quadratic equation ax*x + bx + c = 0 is x = (-b + root of(b*b - 4*a*c) ) / 2 * a. The other root can be obtained by using the minus sign before the ...

### How To: Do normal probability calculations on a calculator

Probability computation is a complex process and even using a calculator can be difficult. But normal probability calculations can be performed quickly with the help of calculator once you know how to use it. So when you have to calculate a probability from a normal distribution you can use the functions on your scientific calculator. You can use the normal CDF function from you calculator to compute the area under a normal curve. The function requires lower band and upper band values, the me...

### How To: Solve for the missing ratios or proportions

In this video the tutor shows how to solve the missing ratios or proportions. He explains it with an example, where a number in one of the ratios is missing and he intends to find this value. He shows the example of cross multiplication, where you multiply the values on the either side of the equation diagonally and finally solves the equation which results in the value of the unknown value. This is an introductory video explaining how to use rations and proportions to find missing values.

### How To: Solve temperature subtraction problems (integers)

An educational video from free math tutoring that shows an easy way to calculate differences of temperature. Many times people commit simple mistakes in subtracting temperatures that lead to illogical results. This video explains a very common pitfall and at the same time, clears up an important concept in temperature subtraction.

### How To: Find how many toothpicks will be needed to form the nth figure in a sequence

From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps. With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to employ inductive reasoning to determine the number of toothpicks you'll require to generate the nth (e.g., the 50th) figure in a sequence of figures.

### How To: Learn Calculus in 20 minutes

Did you sleep all semester in your Calculus class? Are you just waking up now to realize you have a test on Monday and that you're totally screwed? Well, luckily you can learn an entire semester worth of Calculus in just twenty minutes... or at leasts that's the hope.

### How To: Find the Height of a Trapezoid.

Step by step directions for finding the height of a trapezoid. Video: .

### How To: Find the determinant & area of a parallelogram

In this video, we learn how to find the determinant & area of a parallelogram. The determinant of a 2x2 matrix is equal to the area of the parallelogram defined by the column vectors of the matrix. Graph both of the equations that you are given on the vertical and horizontal axis. After you have all of the coordinates in place, you will be able to plug in the correct numbers to figure out what the answer to the equation in. This is more advanced math, so if you have not done it before, you sh...

### How To: Divide numbers using long division

This video focuses on how to do long division. She starts by dividing 1548 by 26, going incrementally between each value. She first take 26 into the first three numbers of 1548 (154) and gets 5, then takes the remainder of 24 (154-130) and brings down the 8 to get 248. She then divides 248 by 26 to get 9 with a remainder of 14. She then goes into some detail as to how to extract the decimal from the remainder by continuing the long division and adding zeros to the end of the divisor. At the e...

### How To: Compute a square root using the geometric method

With mathematics, as with anything else, not everyone progresses at the same rate. Happily, in the age of Internet video tutorials, this isn't a problem. Those who progress quickly can go beyond what's being taught them and those who are struggling likewise have all the time in the world to catch up. With this free video math lesson, you'll learn how to calculate the value of a square using using geometry.

### How To: Prove cos(a+b)=(cos a)(cos b)-(sin a)(sin b) in trig

Need help proving the cos(a+b) = (cos a)(cos b)-(sin a)(sin b) trigonometric identity? This free video lesson will show you how. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series ...

### How To: Figure out the area of quadrilaterals

Quadrilaterals are four sided shapes that are closed. They are polygons. Quadrilaterals can be classified broadly in two ways. If the quadrilateral has a two pair of parallel sides then it falls in to the parallelogram category. Further now it can be broken down in to other shapes like square, rectangle, rhombus. If it has only one pair of parallel side then it falls into the trapezoid category. To compute the are of a trapezoid first you need to know the lengths of the parallel sides. Add th...

### How To: Improve your math skills with a free Speed Math game

In this tutorial you will see how to use Jimmy's speed math program that he wrote in Flash. A download to the program is included. This is a GREAT way to help your kids or students (or maybe adults?) get better at math.

### How To: Solve word problems involving domain and range

See how to find the domain and range of a function implied by a word problem with this free video math lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutor...

### How To: Use a mean and scatter plot for Statistics

Wondering how to use a mean and scatter plot for statistics? Just follow the few simple steps as below.

### How To: Minimize the sum of squared error for a regression line in statistics

Learn how to minimize the sum of squared error for regression line problems in stats. Whether you need help studying for that next big stats text or just a hand finishing your homework, you're sure to be well served by this four-part free video math lesson from Salman Khan.

### How To: Write a fraction as a decimal

Write a fraction as a decimal

### How To: Derive the equation of a straight line

In this tutorial the instructor shows how to derive a straight line equation. He shows us a process that consists of two steps. In step one he uses the slope formula to obtain the slope of the line which is the ratio of difference of y-coordinates and difference of x-coordinates. Now in the step two he uses the slope he obtained in the first step and equates it two a another slope derivation which uses a generic x, y variables and a real point. Now solving this equation he arrives at the equa...

### How To: Divide and give an answer as a fraction

In this video we learn how to divide and give an answer as a fraction. If you are starting out with a simple fraction, you will simply take the number before the divide sign on the top and the second number on the bottom. If you end up with a number that is able to be simplified, make sure you take it down to it's most simple version possible. You can end up with a top heavy fraction, which means there will be whole numbers involved. Do the division to figure out how many times the bottom num...

### How To: Know if matrices can be multiplied

In this Education video tutorial you will learn how to know if matrices can be multiplied. If the column of the first and the row of the second match, you can multiply them. For example if, matrix A has 2 rows and 3 columns (A: 2x3) and matrix B has 3 rows and 4 columns (B: 3x4), then you can multiply them. But, if A: 3x2 and B: 3x4, you cannot multiply them. The shape of the resultant matrix will be the shape of the outer numbers. For example, we saw that if A:2x3 and B :3x2, then they can b...

### How To: Solve basic linear function word problems in algebra

Need some help solving linear function word problems? See how it's done with this free video math lesson. Need help finding the From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series o...

### How To: Solve a math probability problem with a number cube

In this math lesson we will learn how to solve simple probability problems with a number cube. The probability of an event measures the likelihood that the event will occur.

### How To: Find the volume of a cylinder with given radius

This tutorial, taught by a teacher from Lincoln High School in Los Angeles, CA, will teach you how to find the volume of a cylinder when given its radius.

### How To: Turn multiplication into sum

This is a handy math trick that show you how to turn a multiplication problem into a sum problem. An unusual way to perform a multiplication. You only need to be able to sum, halve and double numbers. It is not efficient, but it is rather intriguing and fun.

### How To: Find if a point lies on a line in point slope form

In this tutorial, the author shows how to determine if a point lies on a given line which is in Point Slope Form. To show the method he takes a sample point order pair and an equation of a line in its point slope form. Now he substitutes the value of the x, y order pair and the equation of the line, and solves the equation on both the sides. If both sides match it means that the point lies on the given line, or else it does not lie on the current line. In this video, the instructor shows how ...

### How To: Calculate percentage growth rates in calculus

Want to calculate percentage growth rates (also known as the relative rates of change)? Learn how with this free video calculus lesson, which covers calculating the percentage growth rate using a logarithmic derivative, elasticity of demand and the relation between elasticity of demand and revenue. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever t...

### How To: Solve a system of linear inequalities via elimination

From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to solve a system of linear inequalities by elimination.

### How To: Use an asymptote to find the equation of a hyperbola

Need instruction on how to find the equation of a hyperbola using an asymptote? Learn how with this free video lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

### How To: Use geometric sum to figure out mortgage payments

This video walks you through the steps of using geometric series sum to figure out mortgage payments. This excellent video shows you a clean blackboard, with the instructors voice showing exactly what to do. Don't fret, any question you may have, will be answered. Watching this video will make you feel like your back in the classroom but rather comfortably from your home.

### How To: Solve an equation using the point slope form

In this video the instructor shows how to derive a general equation for a line in Point-Slope form. The slope of an equation is the ratio of difference of y coordinates to the difference of x coordinates. In other words, slope is the change of y up on change of x. So you have the basic slope equation m = (y2 - y1)/(x2 - x1). When you have fractions you can simplify them by multiplying the denominator to the numerator on both sides. So multiply the equation by (x2-x1) on both sides. This gives...

### How To: Understand the CAH formula

In order to find the cosine of a triangle in trigonometry, you will need to understand the CAH formula, part of the larger mnemonic of SOHCAHTOA, which outlines how to find the sine, cosine, and the tangent of an angle. The video offers accurate diagrams as well as examples in order for their viewers to better understand the CAH formula. The CAH formula simply outlines the fact that the cosine is equal to the length of the adjacent side of the triangle over the hypotenuse of the triangle. By ...

### How To: Solve non-linear systems of equations by graphing

From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to solve non-linear systems of equations in algebra.

### How To: Solve problems involving deductive reasoning

From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test). With this installment from Internet pedagogical superstar Salman Khan's series of free math tutorials, you'll learn how to unpack and solve word problems that require you to apply deductive reasoning.

### How To: Simplify cube roots

In this video, the narrator presents the viewer with a quick, painless way of simplifying cube roots. The narrator presents many methods to simplify square roots to appeal to different learning styles. By doing things like dividing the power by the root to figure out the power of a number x, the viewer is better able to tackle square-rooting numbers that may not have friendly roots. The video gets more complex as it goes on, eventually teaching the viewer to split the inside of a root up if t...