Question

\(\frac{1+y}{9}=\frac{1+2y}{7}=\frac{1+3y}{x}\) tinh x

Answer 1

Ta có:

\(\frac{1+y}{9}=\frac{1+2y}{7}\)                                             

\(\Rightarrow\)(1+y)7=(1+2y)9

        7+7y=9+18y

        7-9  =18y-7y

          -2  =11y

          y   = \(\frac{-2}{11}\)

Thay y=\(\frac{-2}{11}\)ta có:

\(\frac{1+\frac{-2}{11}}{9}=\frac{1+3\cdot\frac{-2}{11}}{x}\)

\(\frac{\frac{9}{11}}{9}=\frac{\frac{5}{11}}{x}\)

\(\Rightarrow\)\(\frac{9}{11}\cdot x=\frac{5}{11}\cdot9\)

         \(\frac{9x}{11}=\frac{45}{11}\)

\(\Rightarrow\)9x=45

         x=5

 k mk nha nhớ ghi vậy....