Представте вырожение в виде многочлена

(2x-y) (y+2x) + x (4-3x) ... 5c (c+1) - (b-3c) (b+3x) ... (y-2) (y+2) + (3-y) (3+y)

1) ... = (2 х-у) (2 х+у) + х (4-3 х) = 4 х^2 - y^2 + 4x - 12x^2 = - 8x^2 - y^2 + 4x

2) ... = 5c^2 + 5c - (b^2-9c^2) = 5c^2 + 5c - b^2 + 9c^2 = 14c^2 - b^2 + 5c

3) ... = y^2-4 + 9 - y^2=5