Question

what is the answer to 4a squared minus 16a= negative 15

Answer 1

4a^2 - 16a = -15
4a^2 - 16a + 15 = 0
(2a - 3)(2a - 5) = 0

Now separate the two individual equations, set to zero, and solve...

2a - 3 = 0
2a = 3
a = 3/2

2a - 5 = 0
2a = 5
a = 5/2

Your answers are
3/2 and 5/2