a.
\(x^2-4x+3=0\)
\(\Leftrightarrow x^2-x-3x+3=0\)
\(\Leftrightarrow\left(x^2-x\right)-\left(3x-3\right)=0\)
\(\Leftrightarrow x\left(x-1\right)-3\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-3\right)=0\)
\(\Leftrightarrow x=1;x=3\) là nghiệm
b.
\(2x^2+5x+3=0\)
\(\Leftrightarrow2x^2+3x+2x+3=0\)
\(\Leftrightarrow\left(2x^2+2x\right)+\left(3x+3\right)=0\)
\(\Leftrightarrow2x\left(x+1\right)+3\left(x+1\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(2x+3\right)=0\)
\(\Leftrightarrow x=-1;x=-\dfrac{3}{2}\) là nghiệm
`a) x^2-4x+3`
`= x^2 - x - 3x +3`
`= x(x-1) - 3(x-1)`
`=(x-3)(x-1)`
Cho `(x-3)(x-1) =0`
`<=>`\(\left[{}\begin{matrix}x=3\\x=1\end{matrix}\right.\)
`b) 2x^2+5x+3`
`= 2x^2 + 2x +3x +3`
`=2x(x+1) + 3(x+1)`
`=(2x+3)(x+1)`
cho `(2x+3)(x+1) =0`
`<=>`\(\left[{}\begin{matrix}2x=-3\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{2}\\x=-1\end{matrix}\right.\)
`x^2-4x+3`
`=(x-3).(x-1)`
`(x-3).(x-1)=0`
`@TH1:`
`x-3=0`
`x=0+3`
`x=3`
Vậy `x = 3`
`@TH2:`
`x-1=0`
`x=0+1`
`x=1`
Vậy `x=1`
__________________________________
`2x^2+5x+3`
`(x+1)(2x+3)`
`@TH1:`
`x+1=0`
`x=0-1`
`x=-1`
Vậy `x=-1`
`@TH2:`
`2x+3=0`
`2x=-3`
`x=(-3):2`
`x= (-3)/2`
Vậy `x = (-3)/2`
