f(x) = 9x^2 - 5x + 3 is given. The notation means that wherever you see and x on the right, you replace it with the x in the brackes on the left. f(3) is a direction, not anything you have to adjust or manipulate.
Solution
f(-3) = 9*(-3^2) - 5*(-3) + 3 (-(3))^2 = -3 * -3 = 9 two minuses make a +
f(-3) = 9*(-3)(-3) + 15 + 3 -3 times an operation of minus equals a +
