(3a+2b)^2+(3a-2b)^2-(6a-4b)(3a-2b)=

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(3a+2b)^2+(3a-2b)^2-(6a-4b)(3a-2b)=
(3a+2b)^2+(3a-2b)^2-(6a-4b)(3a-2b)=

(3a+2b)^2+(3a-2b)^2-(6a-4b)(3a-2b)=
(3a+2b)^2+(3a-2b)^2-(6a-4b)(3a-2b)
=(3a+2b)^2+(3a-2b)^2-2*(3a-2b)(3a-2b)
=(3a+2b)^2-(3a-2b)^2
=(3a+2b+3a-2b)[3a+2b-(3a-2b)]
=6a*4b=24ab

(3a+2b)^2+(3a-2b)^2-(6a-4b)(3a-2b)
= 9a^2+12ab+4b^2+9a^2-12ab+4b^2-2(3a-2b)^2
=18a^2+8b^2-2(9a^2-12ab+4b^2)
=24ab

设3a+2b=x,3a-2b=y
则原等式=x^2+y^2-2xy
=(x-y)^2
即(3a+2b-3a+2b)^2 =16b^2