Question

If (a+b+c)= 10, a²+b²+c²=42 then find ab+bc+ca

Answer 1

Answer:

see the attachment and it's answer is 45

Step-by-step explanation:

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Answer 2

Answer:

39

Step-by-step explanation:

Given,

a+b+c=10.....(1)

a²+b²+c²=42..(2)

To find ab+bc+ca

Square eq1 on both side.

(a+b+c)²=(10)²

a²+b²+c²+2ab+2bc+2ca=100

Put the value of eq2

42+2ab+2bc+2ca=100

2ab+2bc+2ca=100-42

2(ab+bc+ca)=58

ab+bc+ca = 58 / 2

ab+bc+ca = 39.

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