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Question
Find the product:
(x + 3) (x + 5) (x + 7)
Sum
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Solution
Given: (x + 3)(x + 5)(x + 7)
Step-wise calculation:
1. First, multiply the first two binomials:
(x + 3)(x + 5) = x2 + 5x + 3x + 15
(x + 3)(x + 5) = x2 + 8x + 15
2. Now multiply this result with the third binomial (x + 7):
(x2 + 8x + 15)(x + 7)
3. Distribute each term in the trinomial by (x) and then by (7):
= (x2)(x) + (8x)(x) + 15(x) + (x2)(7) + (8x)(7) + 15(7)
= x3 + 8x2 + 15x + 7x2 + 56x + 105
4. Combine like terms:
x3 + (8x2 + 7x2) + (15x + 56x) + 105
= x3 + 15x2 + 71x + 105
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Chapter 3: Expansions - Exercise 3A [Page 64]
