\(2x\left(x+2\right)^2-8x^2=2\left(x-2\right)\left(x^2+2x+4\right)\)
\(\Leftrightarrow\)\(2x\left(x^2+4x+4\right)-8x^2=2\left(x^3-8\right)\)
\(\Leftrightarrow\)\(2x^3+8x^2+8x-8x^2=2x^3-16\)
\(\Leftrightarrow\)\(8x=-16\)
\(\Leftrightarrow\)\(x=-2\)
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