Hi all,
Should be an easy one.
Find dy/dx of:
x^2 + y^2 = 49
I would stick with implicit differentiation rather than trying to solve the quadratic equation.
$\displaystyle \frac{d}{dx}(x^2) + \frac{d}{dx}(y^2) = \frac{d}{dx}(49)$
The first and last terms should be easy enough, for the middle term you can differentiate y as though it was x and then multiply by $\displaystyle \frac{dy}{dx}$ (which is the chain rule)
For example $\displaystyle \frac{d}{dx} \left(\frac{1}{3}y^3\right) = y^2 \frac{dy}{dx}$