Question

Giải phương trình:

x³ - x + 24 = 0

Answer 1

\(x^3-x+24=0\)

\(\Leftrightarrow x^3+3x^2-3x^2-9x+8x+24=0\)

\(\Leftrightarrow x^2\left(x+3\right)-3x\left(x+3\right)+8\left(x+3\right)=0\)

\(\Leftrightarrow\left(x+3\right)\left(x^2-3x+8\right)=0\)

\(\Leftrightarrow x=-3\)

Answer 2

Ta có: \(x^3-x+24=0\)

\(\Leftrightarrow x^3+3x^2-3x^2-9x+8x+24=0\)

\(\Leftrightarrow\left(x+3\right)\left(x^2-3x+8\right)=0\)

\(\Leftrightarrow x+3=0\)

hay x=-3