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If a + B + C = 9 and Ab + Bc + Ca = 15, Find: A2 + B2 + C2. - Mathematics

Sum

If a + b + c = 9 and ab + bc + ca = 15, find: a2 + b2 + c2.

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Solution

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

∴ (9)2 = a2 + b2 + c2 + 2 (15)

81 = a2 + b2 + c2 + 30

∴ a2 + b2 + c2 = 81 − 30 = 51

Concept: Application of Formulae
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APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 12 Identities
Exercise 12 (D) | Q 10 | Page 155
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