Right, I have a question here, about the following:
Use implicit differentiation to find the first and 2nd derivative. $$x^{3/5}+y^{3/5} = 7$$
The answer is: $$\begin{align}\frac{dy}{dx} &= -\frac{y^{2/5}}{x^{2/5}} \\[2ex] \frac{d^2y}{dx^2} &= \frac{2x^{3/5}+2y^{3/5}}{5x^{7/5}y^{1/5}} \end{align}$$
Now, I got the $dy/dx$ right, but I just can't the $d^2y/dx^2$ right! I don't know what I'm doing wrong, I differentiated for the 2nd time, I substituted the "$dy/dx$" with the value I got from the first part, continued and still got a different answer.
HELP, a detailed answer would be very helpful! How did the answer turn out to be like that?
Thanks in advance.
Details of the calculus of the second derivative :