Delta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 7 Reply 7, posted (12 years 1 week 3 days 8 hours ago) and read 1191 times:
I think you have misstated the problem. I suspect the question is to solve for dm/dx, which is nothing but the second derivative of y with respect to x.
If the problem is correctly stated, then you must first find x as a function of y.
Since m = dy/dx, you can easily get that by differentiating f(x). Next, substitute for x so you get m as a function of y, not x. Then you can differentiate with respect to y to get dm/dy. But the problem is that getting x as a function of y gets tough if y=f(x) is greater than a first order equation, as in your example.