For this standard for, a = -1, b = 0 and c = 18.
In order to find this, you must first multiply the two parenthesis by each other.
(5 + x)(5 - x)
25 + 5x - 5x - x^2
25 - x^2
Now we need to set it equal to the other side and solve for 0.
25 - x^2 = 7 ----> subtract 7 from both sides.
18 - x^2 = 0 -----> now readjust the order
-x^2 + 18 = 0
So, once we've reached here, the a value is always the coefficient of the x^2 term (-1), b is the value of the coefficient of the x term (0) and c is the constant (18).
