Question

Giải phương trình

5x^3 - 2x^2 - 7x = 0

Answer 1

\(5x^3-2x^2-7x=0\\ \Leftrightarrow x\left(5x^2-2x-7\right)=0\\ \Leftrightarrow x\left[\left(5x^2+5x\right)-\left(7x+7\right)\right]=0\\ \Leftrightarrow x\left[5x\left(x+1\right)-7\left(x+1\right)\right]=0\\ \Leftrightarrow x\left(5x-7\right)\left(x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{7}{5}\\x=-1\end{matrix}\right.\)

Answer 2

x=0x=75x=−1

 

Answer 3

5x3−2x2−7x=0⇔x(5x2−2x−7)=0⇔x[(5x2+5x)−(7x+7)]=0⇔x[5x(x+1)−7(x+1)]=0⇔x(5x−7)(x+1)=0⇔⎡⎢ ⎢ ⎢⎣x=0x=75x=−1