\(\frac{x+3}{y+5}=\frac{x+5}{y+7}=\frac{x+5-x-3}{y+7-y-5}=\frac{2}{2}=1\)
\(x+3=y+5\Leftrightarrow x-y=5-3=2\)
Ap dung tinh chat day ti so bang nhau :
\(\frac{x+3}{y+5}=\frac{x+5}{y+7}\Rightarrow\left(x+3\right)\left(y+7\right)=\left(y+5\right)\left(x+5\right)\)
\(\Rightarrow xy+7x+3y+21=xy+5x+5y+25\)
\(\Rightarrow7x+3y=5x+5y+25-21\)
\(7x-5x=5y-3y+4\)
\(2x=2y+4\Rightarrow2x-2y=4\)
\(2\left(x-y\right)=4\Rightarrow x-y=4:2=2\)
Vay :x-y=2
**** nhe
(x+3)/(y+5)=(x+5)/(y+7)
(x+3)(y+7)=(y+5)(x+5)
x(y+7)+3(y+7)=y(x+5)+5(x+5)
xy+7x+3y+21=xy+5y+5x+25
7x+3y+21=5y+5x+25
(7x-5x)-(5y-3y)=25-21
2x-2y=4
2(x-y)=4
x-y=4/2
x-y=2
