Given function :
f(x)=2x^2+7
Let the function be equal to y :
y=2x^2+7
Now, to find the inverse of the function, find the function for x in terms of y.
y-7=2x^2
x^2=\frac{y-7}{2}
x=\sqrt{\frac{y-7}{2}}
Hence, the inverse of the function is :
f^{-1}(x)=\sqrt{\frac{x-7}{2}}