Question

Tìm x biết:

2x² +10x =0

x² +2x -8=0

Answer 1

\(2x^2+10x=0\\ \Leftrightarrow2x\left(x+5\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=0\\x+5=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=-5\end{matrix}\right.\)

\(x^2+2x-8=0\\ \Leftrightarrow x^2+2x+1-9=0\\ \Leftrightarrow\left(x+1\right)^2=9\\ \Rightarrow\left[{}\begin{matrix}x+1=3\\x+1=-3\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=2\\x=-4\end{matrix}\right.\)