Question

verify the (a+b+c) (a^2+b^2+c^2-ab-bc)-(a)=a^3+b^3+c^3-3abc

Answer 1

Checkout the above attachment !!

Here we extend the identities by multiplication, then do cancelled the terms which were cancelling out .

And we left with a³+b³+c³-3abc on left hand side.

And proved LHS=RHS