Question

HẾT Ạ

Answer 1

7) \(\dfrac{a}{b}=\dfrac{c}{d}\)

\(\Rightarrow\dfrac{b}{a}=\dfrac{d}{c}\)

\(\Rightarrow\dfrac{b}{a}+1=\dfrac{d}{c}+1\)

\(\Rightarrow\dfrac{a+b}{a}=\dfrac{c+d}{c}\)

\(\Rightarrow\dfrac{a}{a+b}=\dfrac{c}{c+d}\left(đpcm\right)\)

9) \(\dfrac{a}{b}=\dfrac{c}{d}\)

\(\Rightarrow\dfrac{a}{c}=\dfrac{b}{d}=\dfrac{a+b}{c+d}=\dfrac{a-b}{c-d}\)

\(\Rightarrow\dfrac{a-b}{a+b}=\dfrac{c-d}{c+d}\left(đpcm\right)\)