Question

If a+b+c=11 ans ab+bc +ca =38 find the value of a2+b2+c2

Answer 1

(a+b+c)2=a2+b2+c2+2(ab+bc+ca)
=(11)2=a2+b2+c2+2*38
=121=a2+b2+c2+76
=a2+b2+c2=121-76=45