PSAT Math : How to multiply rational expressions

Example Questions

Example Question #2 : Rational Expressions

Simplify (4x)/(x– 4) * (x + 2)/(x– 2x)

(4x+ 8x)/(x+ 8x)

4/(x + 2)2

x/(x + 2)

x/(x – 2)2

4/(x – 2)2

4/(x – 2)2

Explanation:

Factor first.  The numerators will not factor, but the first denominator factors to (x – 2)(x + 2) and the second denomintaor factors to x(x – 2).  Multiplying fractions does not require common denominators, so now look for common factors to divide out.  There is a factor of x and a factor of (x + 2) that both divide out, leaving 4 in the numerator and two factors of (x – 2) in the denominator.

Example Question #3 : Rational Expressions

what is 6/8 X 20/3

120/11
3/20
18/160
5
9/40