Ta có: P = \(8x^3-5-\left(2x+1\right)\left(4x^2-2x+1\right)=8x^3-5-\left(8x^3+1\right)=-6\)

Vậy, biểu thức P không thuộc x

\(\left(3x-1\right)^2+\left(x+3\right)^2-10\left(x+1\right)\left(x-1\right)=0\)

\(\Leftrightarrow9x^2-6x+1+\left(x+3\right)^2-10\left(x+1\right)\left(x-1\right)=0\)

\(\Leftrightarrow9x^2-6x+1+x^2+6x+9-10\left(x+1\right)\left(x-1\right)=0\)

\(\Leftrightarrow9x^2+1+x^2+9-10\left(x+1\right)\left(x-1\right)=0\)

\(\Leftrightarrow10x^2+1+9-10\left(x+1\right)\left(x-1\right)=0\)

\(\Leftrightarrow20=0\)

Không có nghiệm nhé !!