For a limit to exist, the limit from the left must equal the limit from the right. Your table above demonstrates this idea of "approaching" from one side and then the other. To write this idea mathematically we write: Iflimxa-f(x)=limxaf(x)=L then limxaf(x)=LLet's practice finding these one-sided limits: Use the graph of f(x) below....(-4)=(-1)=(0)=(4)=a)limx2f(x)=limx2-f(x)=limx2f(x)=b)limx-4f(x)=limx-4-f(x)=limx-4f(x)=c)limx4f(x)=limx4-f(x)=limx4f(x)=d)limx1f(x)=limx1-f(x)=limx1f(x)=2