Answer: 8.
- A 6
- B 7
- C 8
- D 9
Correct answer: C. 8
Explanation: Sum = 2<sup>3</sup> = 8. (Or: 1+3+3+1 = 8).
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