Question

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

Answer 1

Answer:

40

Step-by-step explanation:

as , (a+b+c)^2= a2+b2+c2+2ab+2bc+2ac

and a+b+c=12

therefore, (12)^2=144

so, 144=a2+b2+c2+2ab+2bc+2ac

and a2+b2+c2=64

therefore, 144=64+2ab+2bc+2ac

so, 80=2(ab+bc+ac)

therefore, ab+bc+ac=40