f(3) is equal to 23.
In order to solve for f(3), you must put 3 in for all values of x. This is what the notation of the 3 being in parenthesis means. So we take the original and place 3 in every time we see x.
f(x) = [tex] 2x^{2} + 5 \sqrt{x - 2} [/tex]
f(3) = [tex] 2(3)^{2} + 5 \sqrt{(3) - 2} [/tex]
f(3) = [tex] 2(9) + 5 \sqrt{1} [/tex]
f(3) = [tex] 18 + 5(1) [/tex]
f(3) = [tex] 18 + 5 [/tex]
f(3) = [tex] 23 [/tex]
