Question

Tìm x

\(2x^3+5x^2-12x=0\)

Answer 1

\(2x^3+5x^2-12x=0\\ \Leftrightarrow x\left(2x^2+5x-12\right)=0\\ \Leftrightarrow x\left[\left(2x^2+8x\right)-\left(3x+12\right)\right]=0\\ \Leftrightarrow x\left[2x\left(x+4\right)-3\left(x+4\right)\right]=0\\ x\left(2x-3\right)\left(x+4\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{3}{2}\\x=-4\end{matrix}\right.\)

Answer 2

2x³ + 5x² - 12x = 0
<=> x(2x² + 5x - 12) = 0
<=> x(2x² + 8x - 3x - 12) = 0
<=> x[2x(x + 4) - 3(x + 4)] = 0
<=> x(x + 4)(2x - 3) = 0
   1) x = 0
    2) x = -4 
    3) x =  3/2