Implicit differentiation, whats going wrong!? Hey people can someone point out to me please where I'm going wrong with part B of this question, can't get it to look the answer in the book, d2y/dx2 = -3(x^6/y^7)- 3(x^2/y^3). My answer is listed below under part B section, but i can't manipulate it to look like the above answer :S, any help/tips greatly appreaciated cheers, 5. Implicit Differentiation. If x^4 + y^4 = 16, use the following steps to find y''. (a) Use implicit differentiation to find y', dy/dx = -x^(3)/y^(3) - too easy (b) Use the quotient or product rule to differentiate the expression for y' from part (a). Express your answer in terms of x and y only. d^2/dx^2= ((-x^(3))/(-3y^(4)))*y''-(3x^(2))/(y^(3)) (c) Use the fact that x and y must satisfy x4 +y4 = 16 to simplify your answer to part (b) to the following expression d2y/dx2 = -48(x2/y7).