Question

ab+bc+ca=8 and a2+b2+c2=20 then 1/2(a+b+c)

Answer 1

Answer:

if ab+bc+ca=8

2a +2b +2c=20

Taking 2 as common we get

2(a+b+c)=20

a+b+c=20/2=10

Answer 2

Answer: (a+b+c)²=a²+b²+c²+2ab+2bc+2ca

= 20+8×2=36

Thus a+b+c= 6

Thus a+b+c/2= 3

Note: it might be given ±3. This is because √36 is ±6. So it is actually ±3. But if you are in class 10 or below, then the answer is 3.

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