/==(2A+B-C)^2==

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/==(2A+B-C)^2==/==(2A+B-C)^2==/==(2A+B-C)^2==/=(X^3+3X^2Y+3XY^2+Y^3-X^3-Y^3)/(3(X+Y))=(3X^2Y+3XY^2)/

/==(2A+B-C)^2==
/
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=
(2A+B-C)^2
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=

/==(2A+B-C)^2==
/
=(X^3+3X^2Y+3XY^2+Y^3-X^3-Y^3)/(3(X+Y))
=(3X^2Y+3XY^2)/(3(X+Y))
=(3(X+Y))XY/(3(X+Y))
=XY
(2A+B-C)^2= 2A(2A+B-C)+B(2A+B-C)-C(2A+B-C)
=4A^2+B^2+C^2+4AB-4AC-2BC