The Attempt at a Solution
I found the partial derivatives from the equation. I am stuck at finding the critical points from the first two fx(x,y) and fy(x,y). I equaled 0=6x^2+y^2+25x and solved for y^2. I then got y^2=-6x^2-25x and tried substituting it in, fy(x,y)= 2x(6-x^2-25x)^2+2(-6x^2-25x)^2. which did not work out well as I was able to do in similar problems.