Question 137853
You are given a function {{{f(x)=x^2+2x}}}

You then asked to evaluate that function at f(-1). 

All you need to do it substitute {{{-1}}} for x everywhere in the function and then simply the result.

{{{f(x)=x^2+2x}}}
{{{f(-1)=(-1)^2+2*(-1)}}}
{{{f(-1)=1 + (-2)}}}
{{{f(-1) = 1 - 2}}}
{{{f(-1) = -1 }}}

So given an input of {{{-1}}}, the function evaluates to {{{-1}}}. 

Now let's find f(2)
{{{f(x)=x^2+2x}}}
{{{f(2)=(2)^2+2*(2)}}}
{{{f(2)=4 + 4)}}}
{{{f(2) = 8}}}

And so on.

Get it?