Sample 1 — One-mark MCQ
Question 1 · Sequences, subsequences and exponential limits
- Official locator
- Section A · Question 1 · MCQ · 1 mark (opens the official paper and final key page in a new tab)
- Review record
- Independent mathematical and source-expression review passed on 29 July 2026. Use with official Q1; no official prompt or option text is included. Reviewed at .
Summary
Classify a parity-driven sequence and an exponential-type sequence using two different convergence tests. Keep the official Q1 open; this summary does not restate its prompt or answer choices.
Core idea
Split the oscillatory sequence into even and odd subsequences, then use a logarithmic or standard exponential limit for the second sequence.
Derivation
- 1Separate the first sequence into its even-indexed and odd-indexed subsequences.
- 2Their limits are 0 and 2, so the full first sequence cannot converge.
- 3Take logarithms of the second sequence to convert its power into a product.
- 4Apply the limit log(1+x)/x → 1 to obtain the exponent 3/2.
- 5Exponentiation gives the second limit e^(3/2), and the two derived classifications select letter D.
Final result
D — the first sequence diverges, while the second converges to e^(3/2).
Verification
Rewrite the second expression as a 3/2 power of a standard sequence tending to e; this independently returns e^(3/2).
Common pitfall
A vanishing correction does not remove a fixed parity oscillation. Check subsequences before applying a single-limit rule.





