`x^9 - x^7 - x^6 - x^5 + x^4 + x^3 + x^2 - 1`
` = (x^9 - x^8 + 11x^7 + 7x^6 + 11x^5 + 7x^4 + x^3 - x^2) + (x^8 - x^7 + 11x^6 + 7x^5 + 11x^4 + 7x^3 + x^2 - x) + (x^7 - x^6 + 11x^5 + 7x^4 + 11x^3 + 7x^2 + x-1)`
` = x^2 (x^7 - x^6 + 11x^5 + 7x^4 + 11x^3 + 7x^2 + x-1) + x(x^7 - x^6 + 11x^5 + 7x^4 + 11x^3 + 7x^2 + x-1) + (x^7 - x^6 + 11x^5 + 7x^4 + 11x^3 + 7x^2 + x-1)`
` = (x^7 - x^6 + 11x^5 + 7x^4 + 11x^3 + 7x^2 + x-1)(x^2 + x + 1)`
` = [(x^7 - x^6 + 10x^5 +8x^4 + x^3 - x^2) + (x^5 - x^4 + 10x^3 + 8x^2 + x-1)] (x^2 + x+1)`
` = [x^2 (x^5 - x^4 + 10x^3 + 8x^2 + x-1) + (x^5 - x^4 + 10x^3 + 8x^2 + x-1)] (x^2 + x+1)`
` = (x^5 - x^4 + 10x^3 + 8x^2 + x-1)(x^2 + 1)(x^2 + x+1)`
` = [(x^5 + 2x^4 + x^3) - (3x^4 - 6x^3 - 3x^2) + (3x^3 + 6x^2 +3x) + (- x^2 - 2x - 1)](x^2+1)(x^2 + x+1)`
` = [ x^3 (x^2 + 3x+1) - 3x^2(x^2+3x+1) + 3x(x^2 + 3x+1) - (x^2 + 2x + 1)] (x^2 + 1)(x^2 + x+1)`
` = (x^3 - 3x^2 + 3x -1) (x^2 + 2x + 1) (x^2 + 1)(x^2 + x+1)`
` = (x-1)^3 (x+1)^2 (x^2 + 1)(x^2 + x + 1)`
