Question

Giải phương trình sau:

x³ - 3x -2 = 0

Answer 1

\(x^3-3x-2=0\)

\(\Leftrightarrow x^3-x-2x-2=0\)

\(\Leftrightarrow x\left(x-1\right)\left(x+1\right)-2\left(x+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(x^2-x-2\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(x-2\right)\left(x+1\right)=0\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}x+1=0\\x-2=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=-1\\x=2\end{array}\right.\)