Solution

The inequality \[(n+1) + \bigl(n^4+2\bigr) + \bigl(n^9+3\bigr) + \bigl(n^{16}+4\bigr) + \cdots + \bigl(n^{10000}+100\bigr) > k\] is true for all \(n\ge 1\). It follows that

  1. \(k < 1300\),

  2. \(k^2<101\),

  3. \(k \ge 101^{10000}\),

  4. \(k < 5150\).

To make this a lot simpler, note that the expression \[(n+1) + \bigl(n^4+2\bigr) + \bigl(n^9+3\bigr) + \bigl(n^{16}+4\bigr) + \cdots + \bigl(n^{10000}+100\bigr)\] increases as \(n\) increases, so the inequality holds for all \(n \ge 1\) if it holds for \(n = 1\). So we need \[\begin{align*} &(1+1)+(1+2)+(1+3)+(1+4)+\cdots +(1+100) > k\\ \iff\quad& 2+3+4+5+\cdots +101 > k\\ \iff\quad& \frac{100}{2}(2+101) > k\\ \iff\quad& 5150 > k. \end{align*}\]

Hence the answer is (d).

Alternatively, we could have broken up the sum here as \[(1+1+\cdots+1)+(1+2+\cdots+100)=100+\tfrac{1}{2}\times100\times101.\]