-4a^2+12ax-9 (a-2b)^2-14(a-2b)+49 (a+b)^2-4ab (x-y)^2-4(x-y-1)

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-4a^2+12ax-9(a-2b)^2-14(a-2b)+49(a+b)^2-4ab(x-y)^2-4(x-y-1)-4a^2+12ax-9(a-2b)^2-14(a-2b)+49(a+b)^2-4

-4a^2+12ax-9 (a-2b)^2-14(a-2b)+49 (a+b)^2-4ab (x-y)^2-4(x-y-1)
-4a^2+12ax-9 (a-2b)^2-14(a-2b)+49 (a+b)^2-4ab (x-y)^2-4(x-y-1)

-4a^2+12ax-9 (a-2b)^2-14(a-2b)+49 (a+b)^2-4ab (x-y)^2-4(x-y-1)
-4a^2+12a-9
=-(4a²-12x+9)
=-(2a-3)²
(a-2b)^2-14(a-2b)+49
=(a-2b)²-2x7x(a-2b)+7²
=(a-2b-7)²
(a+b)^2-4ab
=a²+2ab+b²-4ab
=a²-2ab+b²
=(a-b)²
(x-y)^2-4(x-y-1)
=(x-y)²-4(x-y)+4
=(x-y-2)²
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