1) F(x)=x^2+2

1)

$$\\F(x)=x^2+2\\\\
F(x^2)=(x^2)^2+2=x^4+2\\\\$$

3)

$$G(x)=3x^2-2x-1

G(a+b)=3(a+b)^2-2(a+b)-1\\\\
G(a+b)=3(a+b)^2-2(a+b)-1\\\\$$

You can expand and simplify this one.   

Dont need #2 anymore