Question

tìm nghiệm của đa thức 

C(x)=(3x-2).(x-4)

D(x)=x^2-9

Answer 1

Đặt \(C\left(x\right)=0\Rightarrow\left(3x-2\right)\left(x-4\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}3x-2=0\\x-4=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=4\end{matrix}\right.\)

Vậy \(x\in\left\{\dfrac{2}{3};4\right\}\)

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Đặt \(D\left(x\right)=0\Rightarrow x^2-9=0\Rightarrow\left(x-3\right)\left(x+3\right)=0\)

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

Vậy \(x\in\left\{-3;3\right\}\)

Answer 2

x ϵ {3;-3}