Inverse of the function of y = x2 + 4x + 4

Y = x² + 4x +4 which nothing but (x+2)².
 Then y = (x+2)²
To find the inverse f⁻¹(x), follow the steps:

Just replace y with x and x with y

x = (y +2)²
OR
√x =√(y +2)²  → √x = y+2  and y = √x  - 2

So f⁻¹(x) = -2+√x