1a) \(\dfrac{7}{x-1}=\dfrac{x+1}{9}\)
\(\Rightarrow\left(x-1\right)\left(x+1\right)=7.9\)
\(\Rightarrow x^2-x+x-1=63\)
\(\Rightarrow x^2-1=63\)
\(\Rightarrow x^2=64\)
\(\Rightarrow x=\pm8\)
Vậy \(\left[{}\begin{matrix}x=8\\x=-8\end{matrix}\right.\).
giúp lần cuối lần sau tự nhìn vào bài này mà nghĩ
Bài 1:
\(\dfrac{7}{x-1}=\dfrac{x+1}{9}\)
\(\Leftrightarrow\left(x-1\right)\left(x+1\right)=63\)
\(\Leftrightarrow x^2-1=63\)
\(\Leftrightarrow x^2=64\Rightarrow x=\pm8\)
Bào 2:
\(\dfrac{x-1}{x-2}=\dfrac{x-2}{x+3}\)
\(\Leftrightarrow\left(x-2\right)^2=\left(x-1\right)\left(x+3\right)\)
\(\Leftrightarrow x^2-4x+4=x^2+2x-3\)
\(\Leftrightarrow7-6x=0\Leftrightarrow6x=7\Rightarrow x=\dfrac{7}{6}\)
