Question

(x+y+3z) ( x²+y² +9z² -xy -3yz -3xz )

Answer 1

Let x be a ,y be b ,3z be c

== ( a + b + c ) ( a^2 + b^2 + c ^2 + ab + bc + ca ) = ( a + b + c ) 1/2{(a - b)22 + (b - c)22 + (c – a)22}