Ta có: \(a^6-a^4+2a^3+2a^2\)
\(=a^4\left(a^2-1\right)+2a^2\left(a+1\right)\)
\(=a^4\left(a-1\right)\left(a+1\right)+2a^2\left(a+1\right)\)
\(=\left(a+1\right)\left[a^4\left(a-1\right)+2a^2\right]\)
\(=\left(a+1\right)\left(a^5-a^4+2a^2\right)\)
\(=a^2\left(a+1\right)\left(a^3-a^2+2\right)\)
\(=a^2\left(a+1\right)\left(a^3+a^2-2a^2-2a+2a+2\right)\)
\(=a^2\left(a+1\right)\left[a^2\left(a+1\right)-2a\left(a+1\right)+2\left(a+1\right)\right]\)
\(=a^2\cdot\left(a+1\right)^2\cdot\left(a^2-2a+2\right)\)