Answer:
3(x + 3)(3x - 2)
Step-by-step explanation:
Given
9x² + 21x - 18 ← factor out 3 from each term
= 3(3x² + 7x - 6) ← factor the quadratic
Consider the factors of the product of the x² term and the constant term which sum to give the coefficient of the x- term
product = 3 × - 6 = - 18 and sum = + 7
The factors are + 9 and - 2
Use these factors to split the x- term
3x² + 9x - 2x - 6 ( factor first/second and third/fourth terms )
3x(x + 3) - 2(x + 3) ← factor out (x + 3) from each term
(x + 3)(3x - 2)
Then
9x² + 21x - 18 = 3(x + 3)(3x - 2) ← in factored form
