If the answer is $\infty$, input infinity;
if the answer is $-\infty$, input -infinity.
Use abs(x) for $|x|$.
Given that $f(x)=|x - 7|$ and $g(x)=3 x + 1$, calculate
(a) $f\circ g(x)$= , its domain is (, )
(b) $g\circ f(x)$= , its domain is (, )
(c) $f\circ f(x)$= , its domain is (, )
(d) $g\circ g(x)$= , its domain is (, )