Chapter 8: Binomial Theorem

(a+b)ⁿ = ∫_r=0ⁿ nCr a^n-rb^r

Q1. Find the 4th term in the expansion of (x + 2)²¹.

Solution

T₄ = 22C3 · x¹⁹ · 2² = 1540 · x¹⁹ µ 4 = 6160x¹⁹

Q2. Find the middle term in (x + y)²¹.

Solution

n = 20 (even), so middle term = T₁₁ = 20C10 · x²¹¹