# Find $\frac {dy}{dx}$ in the following: $x^3 +x^2y + xy^2 +y^3 = 81$
$\begin{array}{1 1} -\large \frac{y^2+2xy+3x^3}{x^2+2xy+3y^2} \\\large \frac{y^2+2xy+3x^3}{x^2+2xy+3y^2} \\ -\large \frac{x^2+2xy+3y^2}{y^2+2xy+3x^3} \\ \large \frac{x^2+2xy+3y^2}{y^2+2xy+3x^3} \end{array}$