Question

Tính  \(\dfrac{2a-5b}{a-3b}\) với \(\dfrac{a}{b}=\dfrac{3}{5}\)

Answer 1

`a/b=3/5=>a=3/5b`

Thay `a=3/5b` vào `[2a-5b]/[a-3b]` có:

     `[2. 3/5b-5b]/[3/5b-3b]`

`=[6/5b-5b]/[3/5b-3b]`

`=[-19/5b]/[-12/5b]`

`=[-19/5]/[-12/5]=19/12`

Answer 2

\(\dfrac{2a-5b}{a-3b}=\dfrac{2\left(\dfrac{a}{b}\right)-5}{\left(\dfrac{a}{b}\right)-3}=\dfrac{2.\dfrac{3}{4}-5}{\dfrac{3}{4}-3}=\dfrac{14}{9}\)