Question
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$(a-2 b-3 c)^2$
$(a-2 b-3 c)^2$
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Answer
$(a-2 b-3 c)^2=[a+(-2 b)+(-3 c)]^2$
$=(a)^2+(-2 b)^2+(-3 c)^2+2(a)(-2 b)+2(-2 b)(-3 c)+2(a)(-3 c)$
$=a^2+4 b^2+9 c^2-4 a b+12 b c-6 a c$
$=(a)^2+(-2 b)^2+(-3 c)^2+2(a)(-2 b)+2(-2 b)(-3 c)+2(a)(-3 c)$
$=a^2+4 b^2+9 c^2-4 a b+12 b c-6 a c$
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