\(x^7+2x^2-3\)
\(=x^7-x^6+x^6-x^5+x^5-x^4+x^4-x^3+x^3-x^2+3x^2-3\)
\(=x^6\left(x-1\right)+x^5\left(x-1\right)+x^4\left(x-1\right)+x^3\left(x-1\right)+x^2\left(x-1\right)+3\left(x+1\right)\left(x-1\right)\)
\(=\left(x-1\right)\left(x^6+x^5+x^4+x^3+x^2+3\left(x-1\right)\right)\)
\(=\left(x-1\right)\left(x^6+x^5+x^4+x^3+x^2+3x+3\right)\)