Question

If a+b+c =12 and a2+b2+c2= 64, find the value of ab+bc+ca?​

Answer 1

Solution :

We know that,

(a + b + c)²

= a² + b² + c² + 2ab + 2bc + 2ca

Given that,

a + b + c = 12

a² + b² + c² = 64

From the above identity, we get

12² = 64 + 2ab + 2bc + 2ca

or, 144 = 64 + 2 (ab + bc + ca)

or, 2 (ab + bc + ca) = 144 - 64

or, 2 (ab + bc + ca) = 80

or, ab + bc + ca = 40

∴ ab + bc + ca = 40 (Ans.)

Answer 2

Answer:

$\huge\underline\mathfrak\purple{Solution}$