Question

if a+b+c =12and a^2+b^2+c^2=64,find the value of ab +bc+ca

Answer 1

a+b+c=12
so
(a+b+c)²=12²=144
a²+b²+c²+2(ab+bc+ca)=144
64+2(ab+bc+ca)=144
ab+bc+ca=(144-64)/2= 80/2=40

Answer 2

Hii there!!

Plz refer to the attachment for the solution.

Hope it helps dear.....