If we divide by x−1, the remainder is?
Question
When 1+3x+5x2+7x3+⋯+99x49 is divided by x−1 the remainder is
- 2000,
- 2500,
- 3000,
- 3500.
Solution
The remainder theorem tells us that when a polynomial p(x) is divided by x−1 then the remainder is p(1), which in this case is 1+3+5+7+⋯+99. This is an arithmetic progression, and so sums to 21×50(1+99)=2500 and the answer is (b).