Question

Answer 1

2: =>(x+2)(x-1)=0

=>x=-2 hoặc x=1

3: =>(x-3)(x+3-2x-1)=0

=>(x-3)(2-x)=0

=>x=3 hoặc x=2

Answer 2

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

Answer 3

  2) x²+x-2=0

\(\Rightarrow\)\(\left\{{}\begin{matrix}x=1\\x=-2\end{matrix}\right.\)

3) x²-9-(2x+1)(x-3)=0

    x²-9-2x²+6x+x-3=0

    (x²-2x²)+6x+x-3-9=0

    -x²+7x-12=0

\(\Rightarrow\)\(\left\{{}\begin{matrix}x=4\\x=3\end{matrix}\right.\)