Question

Find the value of $\frac{a+3b}{a-3b}$ if $\frac{a}{b}=\frac{2}{7}$

Answer 1

$\frac{a}{b}=\frac{2}{7}$

$\frac{a}{3b}=\frac{2}{21}$ multiply both sides by $\frac{1}{3}$

$\frac{a+3b}{a-3b}=\frac{2+21}{2-21}$ by componendo and dividendo theorem

$=\frac{23}{-19}=\frac{-23}{19}$

$\therefore \frac{a+3b}{a-3b}=\frac{-23}{19}$