finverse is the reciprocal
basicallly
first find the inverse then evaluate
to find inverse
1. f(x) turns to y
2. switch x and y
3. solve for y
4. replace y with finverse
f(x)=log2(x+4)
y=log2(x+4)
x=log2(y+4)
x=log2(y+4) means 'x is the power that the base 2 mus be rasied to obtain (y+4)'
2^x=y+4
minus 4 both sides
(2^x)+4=y
replace y with finverse
finverse=(2^x)+4
for 3, evaluate
f⁻¹(3)=(2^3)+4
f⁻¹(3)=(8)+4
f⁻¹(3)=12
answer is 12