Question 436805
A function is something that maps a set of x-values (or inputs) to a set of y-values. Each x-value can only map to at most one y-value, if it has two y-values it is not classified a function.


For example, if {{{f(x) = x^2 + 4}}}, we can substitute x with a number or expression:


{{{f(3) = 3^2 + 4 = 13}}}


{{{f(2k + 1) = (2k+1)^2 + 4 = 4k^2 + 4k + 5}}}.