I have to take the derivative of $\displaystyle \frac{y - 1}{y^2 - y + 1}$:

The solution is $\displaystyle \frac{y^2 - 2y}{(y^2 - y + 1)^2}$ but in my work, the answer will have something to the 4th power on the top which will be impossible to cancel out. What have I done wrong?

Edit: Never mind, I see my mistake