1)
[tex]
(f\circ g)(x)=f(g(x))\\\\
(f\circ g)(x)=f(x^2)\\\\
(f\circ g)(x)=3(x^2)+3\\\\
(f\circ g)(x)=3x^2+3\\\\
(f\circ g)(-3)=3\cdot(-3)^2+3\\\\
(f\circ g)(-3)=3\cdot9+3\\\\
(f\circ g)(-3)=27+3\\\\
\boxed{(f\circ g)(-3)=30}
[/tex]
2)
[tex]
x^2-10=26\\\\
x^2-36=0\\\\
(x-6)(x+6)=0\\\\
\boxed{S=\{-6,6\}}
[/tex]
