F(x+2) is simply F(x) but whenever you see an 'x' replace it with 'x+2'. So when x is say 3, F(x) is F(3) and F(x+2) is F(5). If we draw this out on a graph, we see that this has the effect of shifting the graph of F(x) to the left by 2. Becareful not to get confused, some people may think this is a shift to the right by 2 becasue it is 'plus' 2.