Question

Factor completely: 18x^2 - 21x - 15

Answer 1

First, you need to factor out a 3

Answer 2

That leaves you with 3(6x^2-7x-5)

Answer 3

Then continue factoring 6x^2-7x-5 which gives you 3(2x+1)(3x-5)

Answer 4

That should be your answer

Answer 5

Starting with \(\tt 18x^2-21x-15\)

Bring out your 3:
$$\tt =3(6x^2-7x-5)$$
Find factors that add to -7 but multiply to give you 30 (i.e 6*5):
$$\tt =3\frac{(6x + 3)(6x - 10)}{6}$$
Bring out common terms:
$$\tt =3\frac{(3(2x + 1)2(3x - 5)}{6}$$
Reduce
$$\tt =3(2x + 1)(3x - 5)$$
Done

Answer 6

*give you -30