Question
Expand the following:
$(4 a-b+2 c)^2$
$(4 a-b+2 c)^2$
✓
Answer
$(4 a-b+2 c)^2=(4 a)^2+(-b)^2+(2 c)^2+2(4 a)(-b)+2(-b)(2 c)+2(2 c)(4 a)$
${\left[\therefore a^2+b^2+c^2+2 a b+2 b c+2 c a=(a+b+c)^2\right]}$
$=16 a^2+b^2+4 c^2-8 a b-4 a c+16 c a$
${\left[\therefore a^2+b^2+c^2+2 a b+2 b c+2 c a=(a+b+c)^2\right]}$
$=16 a^2+b^2+4 c^2-8 a b-4 a c+16 c a$
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