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Evaluate: (A2 + B2 + C2 - Ab - Bc - Ca)(A + B + C) - Mathematics

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Question

Evaluate: (a2 + b2 + c2 - ab - bc - ca)(a + b + c) 

Sum

Solution

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

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

= a3 + ab2 + ac2 - a2b - abc - ca2 +a2b + b3 + bc2 - ab2 - b2c  - abc + a2c + b2c + c3 - abc - bc2 - c2

= a3 + b3 + c3 -a2b + a2b - ca2 + a2c + bc2 - bc2 - ab2 + ab2 - abc - abc - abc + ac2 - ac2 + b2c - b2c

= a3 + b3 + c3 - 3abc

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Chapter 11: Fundamental Concepts (Including Fundamental Operations) - Exercise 11 (C)

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Selina Concise Mathematics [English] Class 7 ICSE
Chapter 11 Fundamental Concepts (Including Fundamental Operations)
Exercise 11 (C) | Q 3.11
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