Question

How do you do the quadratic equation when there are only two numbers, such as -5x and 15, not the three needed?

Answer 1

-5x + 15=0

a=0 b=-5 c=15

Now, because the a is in the denominator, you can't have zero. So the quadratic formula wont work.

-5x=-15
x=3

So you solve it another way, usually by factoring.