Question

The polynomial x3 + 4x2 – 9x – 36 has 4 terms. Use factoring by grouping to find the correct factorization.

Answer 1

x3 + 4x2 – 9x – 36

= x^2( x + 4) - 9(x + 4)

= (x + 4)(x^2 - 9)

= (x + 4)(x - 3)(x + 3)

Answer 2

x^3 + 4x^2 – 9x – 36
Factor out common terms in the first two terms and the last two terms
x^2 (x + 4) - 9 (x + 4)
factor out the common term (x + 4)
(x + 4) (x^2 - 9)
Rewrite
(x + 4) ( x^2 - 3^2) 
Use the difference of squares
(x + 4) (x + 3) (x - 3)

Hope this helps :)