I have $y=4(x+2)^3$. So first part of taking the inverse is switching the variables $x$ and $y$ so you'd have $x=4(y+2)^3$. Why does the exponent $3$ get put in front of the square root symbol?
The answer they have here is $y= \sqrt[3]{\dfrac{x}{4}} - 2$
One more chance to state my annoyance that Latex uses "\sqrt[n]{x}" for the nth root: $\sqrt[n]{x}$! This NOT an "exponent 3 in front of a square root", it is the "third root", the inverse of third power: $2^3= 8$ so $\sqrt[3]{8}= 2$.