Question

if a+b+c=6and a2+b2+c2=20,find ab +bc +CA​

Answer 1

Answer:

a²+b²+c²=20

(a+b+c)²-3(ab+BC+ac)=20

6²-3(ab+BC+ac)=20

-3(ab+BC+ac)=20-36

ab+BC+ac=16/3