5x^2 - 22x - 15 = 0
Multiply the first and last number together (5 × -15 = -75).
Find factors of -75 that add to -22 (-25 + 3 = -22).
Expand the middle term using these numbers.
5x^2 - 25x + 3x - 15 = 0
Factor the equation in two groups. You can pull 5x out of 5x^2 - 25x. You can pull 3 out of 3x - 15. In both parts, you should be left with x - 5. Proceed to write the factors of the two groups and the result as a binomial.
(5x + 3)(x - 5) = 0
Solve the two new groups.
5x + 3 = 0
5x = -3
x = -3/5
x - 5 = 0
x = 5
x = -3/5 or x = 5
