Question

If a + b + c = 12 , a2+b2+c2 = 10, then find the value of ab + bc + ca​

Answer 1

Answer:

(a+b+c)

2

=a

2

+b

2

+c

2

+2ab+2bc+2ca

⇒(a+b+c)

2

=a

2

+b

2

+c

2

+2(ab+bc+ca)

Given,

ab+bc+ca=10,a

2

+b

2

+c

2

=16

⇒(a+b+c)

2

=16+2(10)

a+b+c=

16+20

=6