Given:
f(5) for the function -2x² + 2x - 3
usually the value enclosed in a parenthesis in a function is the value of x.
f(x) = -2x² + 2x - 3
So if x = 5 ; then, we simply substitute x by its value
f(5) = -2(5²) + 2(5) - 3
f(5) = -2(25) + 10 - 3
f(5) = -50 + 10 - 3
f(5) = 10 - 50 - 3
f(5) = 10 - 53
f(5) = -43
