Đặt:\(3x^2+5x-8=0\)
\(\Leftrightarrow3x^2-3x+8x-8=0\)
\(\Leftrightarrow3x\left(x-1\right)+8\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(3x+8\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\3x+8=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{8}{3}\end{matrix}\right.\)
Vậy \(x=\left\{1;-\dfrac{8}{3}\right\}\) là nghiệm của đa thức
\(3x^2+5x-8\)
\(3x^2+5x-8=0\)
\(\Leftrightarrow3x^2-3x+8x-8=0\)
\(\Leftrightarrow3x\left(x-1\right)+8\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(3x+8\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\3x+8=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{-8}{3}\end{matrix}\right.\)
Tìm nghiệm đa thức: 3x2 + 5x - 8
Ta có: 3x2 + 5x - 8 = 0
\(\Leftrightarrow\) 3x2 - 3x + 8x - 8 = 0
\(\Leftrightarrow\) 3x(x - 1) + 8(x - 1) = 0
\(\Leftrightarrow\) (x - 1) (3x + 8) = 0
\(\Leftrightarrow\) x - 1 = 0; 3x + 8 = 0
\(\Leftrightarrow\) x = 1; x = -8/3
