Question
Expand the following$:(x - 3y - 2z)^2$
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Answer
Using $(a + b + c)^2$
$= a^2 + b^2 + c^2 + 2ab + 2bc + 2ac$
$(x - 3y - 2z)^2$
$= x^2 + (3y)^2 + (2z)^2 + 2(x)(-3y) + 2(-3y)(-2z) + 2(x)(-2z)$
$= x^2 + 9y^2 + 4z^2- 6xy + 12yz - 4xz.$
$= a^2 + b^2 + c^2 + 2ab + 2bc + 2ac$
$(x - 3y - 2z)^2$
$= x^2 + (3y)^2 + (2z)^2 + 2(x)(-3y) + 2(-3y)(-2z) + 2(x)(-2z)$
$= x^2 + 9y^2 + 4z^2- 6xy + 12yz - 4xz.$
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