Ok so i got a mathematica assignment that asks "Find and classify the critical points of [tex]f(x,y)= 5-10xy-4x^2+3y-y^4[/tex] What does this mean lol. The assignment was from 3 weeks ago and i just had spring break so my brain is completely outa wack. Does this mean classify the points as concave up and down or what? This is calculus III by the way. If someone can just lol, tell me what im being asked that would be great. In the exercise before it we found fxx and fyy and fxy of a similar equation and then we found fxx*fyy - (fxy)^2. Im so lost lol. What is this partial derivative thing. Whats the fxx partial derivative * fxy - (fxy)^2 all about? I feel so dumb, my high school calculus teacher would be so dissappointed!