​If (a + b + c) = 6, $$a^2+b^2+c^2$$​= 2, then ab + bc + ca = ? ​

Correct option is C

Given:

(a+ b+ c) = 6

$$a^2+b^2+c^2$$​= 2,

ab+ bc+ ca= ?

Formula Used: 

$$(a +b+c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca$$  

Solution: 

$$(a +b+c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca$$  

​$$6^2 = 2 + 2 ( ab + bc + ca)$$ 

ab + bc + ca = 36 - 2 

2(ab + bc + ca)= 34 

ab + bc + ca = 17 

​