`(x+2)(1 + x - x^2 + x^3) - (1-x)(1 + x + x^2 + x^3)`
` = (x + x^2 - x^3 + x^4 + 2 + 2x - 2x^2 + 2x^3) - (1 + x + x^2 + x^3 - x - x^2 - x^3 - x^4)`
` = x + x^2 - x^3 + x^4 + 2 + 2x - 2x^2 + 2x^3 - 1 - x - x^2 - x^3 + x + x^2 + x^3 + x^4`
` = (x^4 + x^4) + (-x^3 + 2x^3 - x^3 + x^3) + ( x^2 - 2x^2 - x^2 + x^2) + (x + 2x - x + x ) + (2 - 1)`
` = 2x^4 + x^3 - x^2 + 3x + 1`