If you're factoring, your answer is
(4x - 3)(4x + 5)
You'll work it out this way:
16x^2 + 8x - 15
Since there's no GCF here, you multiply the first and third terms, giving you -240. Your next step is to find two numbers that have a sum of 8 and a product of -240. These numbers are 20 and -12. Plug those in and you've got:
16x^2 + 20x - 12x - 15
From here you divide it into two binomials. These are (16x^2 + 20x) and (-12x - 15).
When you take out the greatest common factors (4x and -3), they become:
4x(4x + 5) - 3(4x + 5)
Then you group what's outside of the parentheses together (4x - 3)
And bring what's inside of the parentheses down (4x + 5).
This brings your answer to
(4x - 3)(4x + 5)
