\((6x+1)^2-2(x+1)^3+2(x-1)(x^2+x+1)=1\)
\(\Leftrightarrow36x^2+12x+1-2\left(x^3+3x^2+3x+1\right)+2\left(x^3-1\right)=1\)
\(\Leftrightarrow36x^2+12x+1-2x^3-6x^2-6x-2+2x^3-2=1\)
\(\Leftrightarrow30x^2+6x-4=0\)\(\Leftrightarrow2\left(15x^2+3x-2\right)=0\)
\(\Leftrightarrow15x^2+3x-2=0\)\(\Leftrightarrow15\left(x+\dfrac{1}{10}\right)^2-\dfrac{43}{20}=0\)
\(\Leftrightarrow15\left(x+\dfrac{1}{10}\right)^2=\dfrac{43}{20}\Leftrightarrow x=\pm\dfrac{\sqrt{129}}{30}-\dfrac{1}{10}\)
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