\(\dfrac{x+1}{9}+\dfrac{x+1}{8}=\dfrac{x+1}{11}+\dfrac{x+1}{12}\)
=> \(\dfrac{x+1}{9}+\dfrac{x+1}{8}-\dfrac{x+1}{11}-\dfrac{x+1}{12}=0\)
( x + 1 ) . ( \(\dfrac{1}{9}+\dfrac{1}{8}-\dfrac{1}{11}-\dfrac{1}{12}\) ) = 0
Ta có thể thấy ( \(\dfrac{1}{9}+\dfrac{1}{8}-\dfrac{1}{11}-\dfrac{1}{12}\) ) > 0
=> x + 1 = 0
x = 0 - 1
x = -1
Vậy x = -1
Giải:
\(\dfrac{x+1}{9}+\dfrac{x+1}{8}=\dfrac{x+1}{11}+\dfrac{x+1}{12}\)
\(\Leftrightarrow\dfrac{x+1}{9}+\dfrac{x+1}{8}-\dfrac{x+1}{11}-\dfrac{x+1}{12}=0\)
\(\Leftrightarrow\left(x+1\right)\left(\dfrac{1}{9}+\dfrac{1}{8}-\dfrac{1}{11}-\dfrac{1}{12}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=0\\\dfrac{1}{9}+\dfrac{1}{8}-\dfrac{1}{11}-\dfrac{1}{12}=0\end{matrix}\right.\)
Vì \(\dfrac{1}{9}+\dfrac{1}{8}-\dfrac{1}{11}-\dfrac{1}{12}\ne0\)
Nên \(x+1=0\)
\(\Leftrightarrow x=-1\)
Vậy \(x=-1\).
Chúc bạn học tốt!
