Question

giá trị cua x thoa man

\(\frac{x+9}{x+5}=\frac{2}{7}\)

Answer 1

<=>(x+9)*7=(x+5)*2

<=>(x+9)7=7(x+9)

=>(x+5)2=2(x+5)

=>7(x+9)=2(x+5)

=>7x+63=2x+10

=>5x-53

=>x=\(\frac{-53}{5}\)

Answer 2

\(\frac{x+9}{x+5}=\frac{x+5+4}{x+5}=1+\frac{4}{x+5}=\frac{2}{7}\)

\(\frac{4}{x+5}=\frac{2}{7}-1=-\frac{5}{7}\)  

\(\frac{4}{x+5}=-\frac{5}{7}\Leftrightarrow4.\left(-7\right)=5\left(x+5\right)\)

\(\Leftrightarrow-28=5x+25\)

\(\Leftrightarrow-28-25=5x\Leftrightarrow5x=-53\Leftrightarrow x=-\frac{53}{5}\)