A function is a rule that you apply to a variable. In this case the variable,x, represents a number and the rules just tells you what to do with the number. For f(4), you do: 6*(4)2 = 242 = 22, so f(4) = 22
Do you think you can do it for the other function? Remember to substitute the number given (2) and apply the rule: 4x^2 x +5
edit: that negative was hard to see: sorry, though if you follow the steps with the correct value the answer works out
May 20

Jose S.