Question

Tìm nghiệm của đa thức sau :

a) Q(x) = x² + x

b) N(x) = x² - 4

c) H(x) = 8 - 3x

d) g(x) = x² - 3x

Answer 1

a) \(Q\left(x\right)=x^2+x=0\)

\(\Leftrightarrow x\left(x+1\right)=0\\\Rightarrow \left[{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)

b) \(N\left(x\right)=x^2-4=0\)

\(\Leftrightarrow x^2=4\\ \Leftrightarrow x=\pm2\)

c) \(H\left(x\right)=8-3x=0\)

\(\Leftrightarrow-3x=-8\\ \Leftrightarrow x=\dfrac{8}{3}\)

d) \(g\left(x\right)=x^2-3x=0\)

\(\Leftrightarrow x\left(x-3\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=0\\x-3=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)