Answer: - 4ab³ + b⁴.
- A + 4ab³ + b⁴
- B + 4ab³ - b⁴
- C - 4ab³ - b⁴
- D - 4ab³ + b⁴
Correct answer: D. - 4ab³ + b⁴
Explanation: (a-b)4 = a4 - 4a3b + 6a2b2 - 4ab3 + b4 (alternating signs).
Row n of Pascal's triangle gives the coefficients nC0, nC1, ..., nCn for the expansion of (a+b)ⁿ; each number is the sum of the two numbers diagonally above it, a direct visual proof of the identity nCr = (n-1)C(r-1) + (n-1)Cr.
Concept context
Expansion of (a+b) n , general term, middle term, binomial coefficients, and greatest term