Multiplying fractions are very simple, just multiply the numerators of the fractions to get the new numerator, and multiply the denominators of the fractions to get the new denominator. Let's say we have 2 fractions 1/2 and 1/2 when multiplying them 1/2x1/2=1/4 [1x1/2x2].
Incase you find a negative fraction and a positive fraction [E.g. 1/2 x -1/2] you multiple 1x-1 to get the numerators and 2x2 [Notice that the negative had no impound on the denominator] so by multiplying both fractions we get a final answer equals to -1/4.
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