I am going through some practice problems in Abbott's Analysis text, and one of them is the following: Verify the triangle inequality in the special case where
a) a and b have the same sign;
b) $a \geq 0$, $b < 0$, and $a+b \geq 0$.
I do not know where to begin because I don't know how exactly to go about the 'verification' given such conditions. Thanks!