# How do you find the linear approximation of #f(x,y) = sqrt(53-9x^2-y^2)# at (2,-1)?

##### 1 Answer

Feb 10, 2015

The linear approximation to a function

The equation of that tangent plane depends on the slope in each direction; the partial derivatives

You need to take the partials of your

**Hint:**If you get stuck, look for previous examples of derivatives of a function to a power. Use the Chain Rule to do the job.*

dansmath to the (partial) rescue!