The equation of a curve is $\displaystyle y=\frac{2x}{3x+1}$. The normal to the curve meets the curve at point A(-1,1). Find the equation of the normal.

I am aware that I have to solve this question using the formula $\displaystyle (y-y_1)=\frac{1}{m}(x-x_1)$.

However, I am facing problems in simplifying the equation... I would be grateful if someone would show a detailed workings on it, thanks!