Question 870590
You start with x and you square it to get {{{x^2}}} (eg: let's use x = 12, so {{{x^2 = 12^2 = 144}}}



Then you multiply that result by 6 to get {{{6x^2}}} (6*144 = 864)



Finally, you subtract off 15 from that to get {{{6x^2-15}}} (864 - 15 = 849, so x = 12 leads to f(x) = 849)



Note: you can use any number you want and it doesn't have to be 12.