How do you find absolute and relative error?

For example, one of my homework problems:

Find the linear approximation to f(x)=e^{x}at x=0 and use it to appoximate e^{0.1. }My answers were x+1 and 1.01. I also had to use x+1 to approximate e^{-0.25 }which I got 0.75. I also have to find the absolute and relative error. How would I do this? And which is closer to its corresponding actual value? Why?