Question

If p+q+r=0 then show that (p+r)³= 3pqr

Answer 1

p+q+r=0

= p+q= -r

= (p+q)³= (-r)³

= p³+q³+3p²q+3pq²= -r³

= p³+q³+r³ = -3pq(p+q)


= p³+q³+r³=3pqr