Question

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

Answer 1

Answer:

a+b+C =6

squaring both side

a2+ b2+ c2+ 2(ab+bc+ca) = 36

as we know from question

20+ 2(ab+bc+ca) = 36

2(ab+bc+ca)= 16

ab+bc+ca= 8

Answer 2

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

6^2=20+2(ab+bc+ca)

36-20=2(ab+bc+ca)

16/2=ab+bc+ca

ab+bc+ca=8......

Hope it helps.....