Question

if a^2 +b^2 +c^2= 20 and a+b+c = 0 find an +bc +ca

Answer 1

(a+b+c)2 = a2 + b2+c2+2(ab + bc+ca)

let  (ab + bc+ca) be x

(0)2 = 20 + 2(x)

-20 =2x

-20/2 = x

-10 = x

Therefore ab+ bc+ca = -10

and it's ab not an

Answer 2

hey mate correct ur que it is ab +bc + ca

(a+b+c)2 = a2 + b2+c2+2(ab + bc+ca)

let  (ab + bc+ca) be x

(0)2 = 20 + 2(x)

-20 =2x

-20/2 = x

-10 = x

Therefore ab+ bc+ca = -10