Question

Tìm x biết : x² + x = 2

Answer 1

\(x^2+x=2\)\(\Leftrightarrow x\left(x+1\right)=2\)

\(\Leftrightarrow x\left(x+1\right)=1.2\)

\(\Leftrightarrow x=1\)

Answer 2

Ta có:\(x^2-x=2\Leftrightarrow x^2-x-2=0\Leftrightarrow x^2-2x+x-2=0\Leftrightarrow x\left(x-2\right)+\left(x-2\right)=0\Leftrightarrow\left(x+1\right)\left(x-2\right)=0\Leftrightarrow\left[{}\begin{matrix}x+1=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=2\end{matrix}\right.\)Vậy phương trình có tập nghiệm là \(S=\left\{-1;2\right\}\)