a, \(x^2-x-30=0\)
\(\Leftrightarrow x^2-6x+5x-30=0\)
\(\Leftrightarrow x\left(x-6\right)+5\left(x-6\right)=0\)
\(\Leftrightarrow\left(x+5\right)\left(x-6\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+5=0\\x-6=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-5\\x=6\end{matrix}\right.\)
Vậy x = -5 hoặc x = 6
\(x^2-x-30=0\)
\(x^2+5x-6x-30=0\)
\(x\left(x+5\right)-6\left(x+5\right)\)
\(\left(x-6\right)\left(x+5\right)=0\)
\(\Rightarrow x-6=0\Rightarrow x=6\)
\(\Rightarrow x+5=0\Rightarrow x=-5\)
a) \(x^2-x-30=0\)
\(\left(x-6\right)\left(x+5\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=6\\x=-5\end{matrix}\right.\)
b) \(-2x^2-4x+2=0\)
\(\left(x+1-\sqrt{2}\right)\left(x+1+\sqrt{2}\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-1+\sqrt{2}\\x=\sqrt{-1-\sqrt{2}}\end{matrix}\right.\)
