ax-by
x3+xy
11a-12b
6x2y-5xy2
-x-y
-xyz-abc
a2x3-b2y4
108
606
a-b+c
ax+b+2
xy+yz-zx
3p+2q-5r
x2-y2-z2
7a2+8b2-5c2
(x+y)2+2(x+y)(x-y)+(x-y)2
(2a+3b)2-2(2a+3b)(3b-a)+(3b-a)2
(3x2+7y2)2+2(3x2+7y2)(3x2-7y2)+(3x2-7y2)2
(8x+y)2-(16x+2y)(5x+y)+(5x+y)2
(5x2-3x-2)2+(2+5x2-3x)2-2(5x2-3x-2)(2+5x2-3x)