Question

tìm nghiệm của B(x)
B(x)=2x³ -18x

Answer 1

\(B\left(x\right)=2x^3-18x=0\)

\(\Leftrightarrow2x\left(x^2-9\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\x^2-9=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\pm3\end{matrix}\right.\)

Answer 2

Xét B(x)=0

⇒ 2x³- 18x = 0

⇒2x (x² - 9 ) = 0

⇒\(\left\{{}\begin{matrix}2x=0\\x^2-9=0\end{matrix}\right.\)

⇒\(\left\{{}\begin{matrix}x=0:2\\x^2=0+9\end{matrix}\right.\)

⇒\(\left\{{}\begin{matrix}x=0\\x^2=9\end{matrix}\right.\)

⇒\(\left\{{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)