The problem is to estimate $\displaystyle y + \Delta{y}$ given that $\displaystyle y = x^2 - 5x$, x = 4, and $\displaystyle \Delta{x} = 0.01$

I have tried this and found that the approximate change in y is dy = 0.03 and the actual change in y is 0.0301, but I am not sure what to do with this information.