Daniel O. answered 02/12/13
Math and Physics Tutor, with a math and physics degree
I think you have the function f(x)= 4 - 2x2 and you want to evaluate it for when x = 4. If so, you're finding f(4), so you'd plug in 4 as x, like so:
f(4) = 4 - 2*22 = ?