The surface given by x = x^2 - y^2 is cut by a plane give by y = 3x. producing a curve in the plane. Find the slope of this curve at the ppoint (1,3,-8) A) 3 B) -16 C) - 8sqrt(2/5) D) 0 E) 18/sqrt(10) So we want to look at this curve when y = 3x. Then x = x^2 -y^2 becomes x = x^2 - (3x)^2 which gives x = x^2 - 9x^2. So we have x = -8x^2 or -8x^2 - x = 0. The derivative is then - 16x - 1. At the point (1,3,-8) we should should have the derivative equal to -17 which is not a choice.. Can someone tell me if I did something wrong.