Question

If a + b + c =12 and a²+b²+c²=100,find the value of ab+bc+ca
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Answer 1

Answer:

we know that,

(a+b+c)² = a²+b²+c²+2(ab+bc+ca)

Here,

12² = 100 + 2( ab+ bc+ ca)

=> ab + bc + ca = 44/2 = 22

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Answer 2

Answer:

ab + bc + ca = 22

Step-by-step explanation:

(a + b + c)² = a² + b² + c²+ 2ab + 2bc + 2ca

Using a + b + c =12 and a²+b²+c²=100 in the above equation,

12² = 100 + 2(ab + bc + ca)

2(ab + bc + ca) = 12² - 100

2(ab + bc + ca) = 144 - 100

2(ab + bc + ca) = 44

ab + bc + ca  = 44 /2

ab + bc + ca = 22