Question

If a+b+c=9 and ab+bc+ca=26, what is the value of a^3+b^3+c^3-3abc

Answer 1

Answer:

Given a+b+c=9 & ab+bc+ca=26

As a 3 +b 3 +c −3abc=(a+b+c)(a 2 +b 2 +c 2 −ab−bc−ca)

⇒(a 3 +b 3 +c 3 −abc)=(a+b+c)[(a+b+c)

2 −3(ab+bc+ca)]

⇒(a 3 +b 3 +c 3 −3abc) =9[81−78]

= 27