So I am trying to find the slope of the tangent line to the curve

$$\sqrt{4x+2y} + \sqrt{xy} = \sqrt{38} + \sqrt{24}.$$

at the point $(8,3)$.

I ended up implicitly differentiating and getting $\mathrm dy/\mathrm dx$ on one side and then plugging $(8,3)$ in place of $x$ and $y$ respectively.

I ended up getting a slope of $.644341944$; however, that is incorrect. I am unsure what I did wrong now and how to properly do then problem now then :/

Thanks for the help.

  • 1
    $\begingroup$ Please show the work you have done so we can help spot where you may have made a mistake $\endgroup$ – Mufasa Jun 1 '14 at 19:39


$$\frac2{\sqrt{4x+2y}}dx+\frac1{\sqrt{4x+2y}}dy+\frac y{2\sqrt{xy}}dx+\frac x{2\sqrt{xy}}dy=0\implies$$

$$\left(\frac1{\sqrt{4x+2y}}+\frac12\sqrt\frac xy\right)dy=-\left(\frac2{\sqrt{4x+2y}}+\frac12\sqrt\frac yx\right)\implies$$

$$\frac{dy}{dx}=-\frac{\left(\frac2{\sqrt{4x+2y}}+\frac12\sqrt\frac yx\right)}{\left(\frac1{\sqrt{4x+2y}}+\frac12\sqrt\frac xy\right)}\implies$$



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