If
lim f(x)=0 calculate the following:
x→+∞
lim (f(x)+sinf(x))/(f^4 (x)-2f^3 (x))
x→+∞
If, as you seem to be saying, you have never seen a "limit" before and have no idea what to do, then you have no business attempting this problem! Chrisnew is hoping that is NOT the case and wanting to know what you do know so that we can help you.