Câu hỏi của Ran Mori

Question

Tìm nghiệm đa thức sau

a)$x^2+4x+3$
b)$3x^2-7x+4$

Aki Tsuki · Accepted Answer

a/ $x^2+4x+3=0$

$\Leftrightarrow x^2+x+3x+3=0$

$\Leftrightarrow x\left(x+1\right)+3\left(x+1\right)=0$

$\Leftrightarrow\left(x+1\right)\left(x+3\right)=0$

$\Leftrightarrow\left[{}\begin{matrix}x+1=0\x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-1\x=-3\end{matrix}\right.$

Vậy......

b/ $3x^2-7x+4=0$

$\Leftrightarrow3x^2-3x-4x+4=0$

$\Leftrightarrow-3x\left(x-1\right)-4\left(x-1\right)=0$

$\Leftrightarrow\left(x-1\right)\left(-3x-4\right)=0$

$\Leftrightarrow\left[{}\begin{matrix}x-1=0\-3x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\x=-\dfrac{4}{3}\end{matrix}\right.$

vậy...Câu trả lời: a/ $x^2+4x+3=0$