Question

Kahn Academy Question, Please help!

Answer 1

`g\circ f(-9)=g(f(-9))`

By definition of
`f`,

`f(-9)=3\cdot9-8=19`

and by definition of
`g`,

`g\circ f(-9)=g(f(-9))=g(19)=√(14-19)-10=√(-5)-10`

which is undefined if
`f,g` are supposed to be real-valued functions. If they're complex-valued, then
`√(-5)=i\sqrt 5` and
`g\circ f(-9)=-10+i\sqrt 5`.