Answer
The statement is false.
To make it true,
on the RHS, replace $-\displaystyle \frac{2}{b}$ with $\displaystyle \frac{6}{b}$.
Work Step by Step
When one denominator is the opposite, or additive inverse of the other,
first multiply either rational expression by $\displaystyle \frac{-1}{-1} =1,$
to obtain a common denominator.
$\displaystyle \frac{4}{b}-\frac{2}{-b}= \displaystyle \frac{4}{b}-\frac{2}{-b}\times\frac{-1}{-1}$
$=\displaystyle \frac{4}{b}-\frac{-2}{b}$
$=\displaystyle \frac{4}{b}+\frac{2}{b}$
$=\displaystyle \frac{6}{b}$
The statement is false.
To make it true,
on the RHS, replace $-\displaystyle \frac{2}{b}$ with $\displaystyle \frac{6}{b}$.
