Question

Derivative problem, adding equation into reply

Answer 1

\[\frac{\mathrm{d} }{\mathrm{d} y}\frac{y}{4} + \frac{\mathrm{d} }{\mathrm{d} y}\frac{\ y}{\ 4} \ln(\frac{4}{y})\]

Answer 2

OK, take each derivative separately, then add. Is there a section which needs clarification?

Answer 3

Well, according to my mathematics it should compute to \frac{1}{4} + \frac{1}{4}ln(\frac{4}{y})+\frac{y^{2}}{8} but I might be using my product rule wrongly?

Answer 4

\[\frac{1}{4} + \frac{1}{4}\ln(\frac{4}{y})+\frac{y^{2}}{8}\]

Answer 5

Erm... I think you need a chain rule for ln(4/y). Let me check your work...

Answer 6

You got it!

Answer 7

Want, no... the derivative of (4/y) needs to be tacked on to that last term.

Answer 8

So then you get \[\frac{1}{4} + \frac{1}{4}\ln(\frac{4}{y})+\frac{y^{2}}{4}\]

Answer 9

No, the last term should be multiplied by 4 ln(y/4), not just two.