Question

If a+b+c=6, ab+bc+ca=11, find the value of a 3 +b 3 +c 3 -3abc.

Answer 1

Answer:

We know that:

(a+b+c)

2

=a

2

+b

2

+c

2

+2(ab+bc+ca)

(11)

2

=a

2

+b

2

+c

2

+2(36)

a

2

+b

2

+c

2

=121−72

a

2

+b

2

+c

2

=49.

Answer 2

Answer:

We know that:

(a+b+c)

2

=a

2

+b

2

+c

2

+2(ab+bc+ca)

(11)

2

=a

2

+b

2

+c

2

+2(36)

a

2

+b

2

+c

2

=121−72

a

2

+b

2

+c

2

=49.