If you were going to use the quadratic formula to solve the following equation and b=15, what number would you use as the value for the variable 'a'?

-15x+22=12x^2

You would use a = 12

Step-by-step explanation:

The b value is the coefficient that is in front of the x term, that does not have an exponent of 2. It's simply the x term (not the x^2 term)

We're told that b = 15 is used, but we see that - 15 is in front of the x term. To fix this contradiction, add 15x to both sides so that you move the x term to the right side

-15x+22 = 12x^2

-15x+22+15x = 12x^2+15x

22 = 12x^2+15x

Now subtract 22 from both sides to move that term over as well

22-22 = 12x^2 + 15x - 22

0 = 12x^2 + 15x - 22

12x^2 + 15x - 22 = 0

12x^2 + 15x + (-22) = 0

The last equation is in the form ax^2 + bx + c = 0 with

a = 12, b = 15, c = - 22