If you would like to evaluate the function f(x) = -3x^2 - 4x, you can do this using the following steps:
c = -2
x = - 4c = -4 * (-2) = 8
f(x) = -3x^2 - 4x
x = 8
f(8) = -3 * 8^2 - 4 * 8 = -3 * 64 - 32 = -192 - 32 = -224
The correct result would be -224.