1. 5x(x-2y) + 2.(2y-x)^2 = 5x(x-2y) + 2(4y^2 - 4xy + x^2) = 5x^2 - 10xy + 8y^2 - 8xy + 2x^2 = 7x^2 - 18xy + 8y^2
2. 7x( y-4)^2 - ( 4-y)^3 = 7x(y^2 - 8y + 16) - (64 - 48y + 12y^2 - y^3) = 7xy^2 - 56xy + 112x - 64 + 48y - 12y^2 + y^3 = y^3 - 12y^2 + 7xy^2 - 56xy + 48y + 112x - 64
3. 100x^2 - (x^2+25)^2 = 100x^2 - (x^4 + 50x^2 + 625) = 100x^2 - x^4 - 50x^2 - 625 = -x^4 + 50x^2 - 625
4. (x-y+5)^2 - 2(x-y+5) + 15x^2 - xz - 9y^2 + 3yz = (x-y+5)(x-y+5) - 2(x-y+5) + 15x^2 - xz - 9y^2 + 3yz = (x-y+5)^2 - 2(x-y+5) + 15x^2 - xz - 9y^2 + 3yz
5. x^3 -x^2 -5x +125 = x^3 - x^2 - 5x + 125
6. x^3 + 2x^2 -6x -27 = x^3 + 2x^2 - 6x - 27
7. 12x^3 + 4x^2 -27x -9 = 12x^3 + 4x^2 - 27x - 9
8. x^4 -25x^2 + 20x -4 = x^4 - 25x^2 + 20x - 4
9. 4x^4 +4x^3 -x^2 -x = 4x^4 + 4x^3 - x^2 - x