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Question
Simplify:
(3x – 4y)3 + (4y – 5z)3 + (5z – 3x)3
Simplify
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Solution
Given: (3x – 4y)3 + (4y – 5z)3 + (5z – 3x)3
Step-wise calculation:
1. Let a = 3x – 4y, b = 4y – 5z, c = 5z – 3x.
Note that a + b + c = (3x – 4y) + (4y – 5z) + (5z – 3x) = 0.
2. There’s a well-known algebraic identity: If a + b + c = 0, then a3 + b3 + c3 = 3abc.
3. Therefore, (3x – 4y)3 + (4y – 5z)3 + (5z – 3x)3 = 3(3x – 4y)(4y – 5z)(5z – 3x).
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Chapter 3: Expansions - Exercise 3A [Page 65]
