What is the factored form of 4x2 + 23x - 72?

(x + 8) (4x - 9)

using the a-c method

consider the factors of the product 4 * - 72 = - 288 which sum to + 23

The factors are + 32 and - 9

split the middle term using these factors

4x² + 32x - 9x - 72 (factor by grouping)

= 4x (x + 8) - 9 (x + 8)

take out the common factor (x + 8)

= (x + 8) (4x - 9)

Assuming that the first number is four x squared, the answer is: (x+8) (4x-9)