(c-d)^2.
(40+b)^2
(10+8k)^2
(5h-4)^2
(3a+1)^3
(4-a)^3
(b+3)(b-3)
(k-y)+(k+y)
(2c-a)(2c+a)
(8x+4y)(8x-4y)

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