Given that the solutions to a quadratic equation are −7 8, which of the following could represent the quadratic function?

a: x^2+15x+56 x 2 + 15 x + 56
b: x^2-x-56 x 2 − x − 56
c: x^2-15x-56 x 2 − 15 x − 56
d: x^2+x-56 x 2