Question

\(\left(x+3\right)^3-\left(x-1\right)^3=0\)

Giải pt

Answer 1

\(\Leftrightarrow\left(x^3+3x^2.3+3.x.3^2+3^3\right)-\left(x^3-3x^2+3x-1\right)=0\\ \Leftrightarrow\left(x^3-x^3\right)+\left(9x^2+3x^2\right)+\left(27x-3x\right)+\left(27+1\right)=0\\ \Leftrightarrow12x^2+24x+28=0\\ \Leftrightarrow x^2+2x+\dfrac{7}{3}=0\\ \Leftrightarrow\left(x^2+2x+1\right)+\dfrac{4}{3}=0\\\Leftrightarrow\left(x+1\right)^2+\dfrac{4}{3}=0\\ \Leftrightarrow\left(x+1\right)=-\dfrac{4}{3}\left(vô.lí\right)\)

=> Pt vô nghiệm