Answer: 70.
- A 56x
- B 8C4 / x²
- C 70
- D 70/x
Correct answer: C. 70
Explanation: n=8, middle term is T<sub>5</sub>. T<sub>5</sub> = 8C4 x<sup>8-4</sup> x x<sup>-4</sup> = 8C4 = 70. Middle term = 70.
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