Question 482948
Just replace all occurrences of the variable (e.g. x, n) with that number and simplify. For example,


*[tex \LARGE f(x) = 2x^3 + 5x + 1]


*[tex \LARGE f(1) = 2(1)^3 + 5(1) + 1 = 8]


Things get a little different when the function is not in terms of a simple "x." We can define a function g:


*[tex \LARGE g(2x + 1) = 5x^2]


Suppose we want to find the value of g(7). We do not plug in x = 7. Rather we plug in 2x + 1 = 7, which is the same as plugging in x = 3.


*[tex \LARGE g(7) = 5(3)^2 = 45]