Question

[Đặng Ngọc Hà]

Tìm x biết

a) 3x.(x+2).(x-2)-(x+3).(x\(^2\)-3x+9)=6x-27

Answer 1

[DƯƠNG PHAN KHÁNH DƯƠNG]

\(3x\left(x+2\right)\left(x-2\right)-\left(x+3\right)\left(x^2-3x+9\right)=6x-27\)

\(\Leftrightarrow3x^3-12x-x^3-27-6x+27=0\)

\(\Leftrightarrow2x^3-18x=0\)

\(\Leftrightarrow x^3-9x=0\)

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

\(\Leftrightarrow x\left(x-3\right)\left(x+3\right)=0\)

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

Answer 2

[Đặng Ngọc Hà]

HỘ mk nhanh nha