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**Mathnood768** Factor: 3(2z + 3)^2 - 9(2z + 3) - 30

My attempt:

3(2z + 3)^2 - 9(2z + 3) - 30

3x^2 - 9x - 30 Replace (2z +3)^2 and (2z +3) with a variable (I choose x)

3(x^2 - 3x - 10) Find 2 integers whose product is ac = -10 and sum equals b = -3 (+2 and - 5)

3(x^2 + 2x )(- 5x - 10)

x(x + 2) -5(x + 2)

(x - 5) ( x + 2) Plug (2z +3)^2 and (2z +3) back into the x's.

((2z + 3)^2) - 5 ((2z + 3) + 2)

**(2z - 2)(2z + 5)**

I got it wrong, the correct answer is **6(z - 1)(2z + 5)**

Where did I go wrong?