Question

23. * MULTIPLE CHOICE Which is the correct factorization of -45x^2 + 20y^2

A -5(3x + 2y)^2
B 5(3x - 2y)^2
C -5(3x+2y)(3x-2y) D 5(3x+2y)(3x-2y)

Answer 1

c)-5(3x+2y)(3x-2y)

Explanation:

1) lets find out if -45 and 20 have a GCF

-45 and 20 are both dividable by -5 so

-5(9x^2-4y^2)

1) you can see that 9 and -4 are perfect square so:

-5(3x+2y)(3x-2y)

Recheck:

1) lets use FOIL to see if this is right(if its right we will get back our original equation)

-5(9x^2-6xy+6xy-4y^2)

-5(9x^2-4y^2)

-45x^2+20y^2

hope this helps!