Question

if a + b + c = 0 and a square + b square + c square find the value of AB+ BC + CA

Answer 1

heya

there is a small mistake in your answer

a^2 + b^2 + c^2 should be equal to some x number

and it is not mentioned so, let it be 20

for any number process is same


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

let (ab + bc+ca) be x

(0)2 = 20 + 2(x)

-20 =2x

-20/2 = x

-10 = x

There fore , ab+ bc+ca = -10