If you have an equation like x+1. We can say that G(x) = x+1.
So if I say what is G(1)? You just plug in 1 into the equation and solve. So G(1)=1+1 = 2.
So in this problem they give you G(x)=x-3.
Then they say G(F(x))= x^2 -3
That's like what we did above. They plugged in something "f(x)" into G(x) and got x^2 - 3. What can you plug into x-3 to get x^2 - 3? This is F(x). So if you plug in x^2 into x-3 you get x^2-3.
I was thinking the combination 1,5 and 5,1 would count as one combination and same goes for 2,4 and 4,2 so I was only coming up with 3 combinations:
1,5
2,4
3,3
Now it makes sense when you explained. Thanks