if a+b+c+d=0 then(a+d)^2+(b+d)^2+(c+d)^2 is equal to

Opening the bracket terms and seperating the square terms and terms with d would give

a^2+b^2+c^2+3d^2+2d(a+b+c)

But,
a+b+c= -d

So,
a^2+b^2+c^2+3d^2+2d(-d)
and solve ahead to get the answer...
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