inverse of f(x)=sqrt(10-x)
The function is strictly monotone on x ≤ 10: it has an inverse on its range y ≥ 0
Isolate the square root: 10 -x = y, with y ≥ 0. Under this condition, squaring gives 10 -x = y2
⇥Let's solve in ℝ: 10 -x = y2
⇥ⓘ We gather the terms in x on the right and the other terms on the left
⇥ 10 -y2 = x
⇥Solution obtained: x = 10 -y2
Renaming the output as x, the inverse is 10 -x2, with domain x ≥ 0
▶Inverse function:   (10 -x2 for x ≥ 0)