Question 281375
The notation of f(-1) is a tricky one. Basically, you take the -1 and plug it in for all the x's.

For your example:

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

is really

{{{f(-1) = (-1)^2 + 3(-1) + 4}}}

When you square a negative, it is the same thing as multiplying a negative with a negative which turns into positive so:

{{{(-1)^2 + 3(-1) + 4 = 1 -3 + 4 = 2}}}

Basically {{{f(-1) = 2}}}