Question

Tìm x, y biết

7) \(\dfrac{x+5}{7}=\dfrac{-30}{5y+5}=\dfrac{40}{140}\)

Answer 1

Ta có \(\dfrac{x+5}{7}=\dfrac{40}{140}\)

\(\Leftrightarrow\dfrac{x+5}{7}=\dfrac{2}{7}\\ \Leftrightarrow x+5=2\\ \Leftrightarrow x=-3\)

Tương tự : \(\dfrac{-30}{5y+5}=\dfrac{40}{140}\)

\(\Leftrightarrow\dfrac{-6}{y+1}=\dfrac{2}{7}\\ \Leftrightarrow\left(y+1\right)\cdot2=-6\cdot7\\ \Leftrightarrow2y+2=-42\)

\(\Leftrightarrow2y=-44\\ \Leftrightarrow y=-22\)

Vậy..................................