Question

giúp mình với

Answer 1

Bài 4: 

a: Vì m/n=1/5 nên n=5m

\(A=\dfrac{4m-2n}{4m+5n}=\dfrac{4m-10m}{4m+25m}=\dfrac{-6}{29}\)

b: x-y=7

nên x=y+7

\(B=\dfrac{2\left(y+7\right)+7}{3\left(y+7\right)-y}+\dfrac{2y-7}{3y-y-7}\)

\(=\dfrac{2y+21}{2y+21}+\dfrac{2y-7}{2y-7}=2\)