Borui Academy

📚 BC Series Deep-Dive Notes

8 chapters · 56 narrated audio segments (Chinese) · 17 visual diagrams · 85 practice problems

56 audio 17 images 8 chapters
  1. Ch 1

    Sequences

    Limits, L'Hôpital, Squeeze, MBT

    Sequence convergence; L'Hôpital; squeeze theorem; the Monotonic Bounded Theorem; the recursive-sequence three-step playbook.

    6 2
  2. Ch 2

    Series Basics, Geometric & p-Series

    Partial sums, geometric formula, p-series, n-th term, telescoping

    Partial-sum definition; geometric series and convergence; p-series rule; the (one-way) n-th term test; telescoping series.

    7 3
  3. Ch 3

    Convergence Tests Toolkit

    Decision tree + 7 tests

    Decision tree plus integral, comparison, limit-comparison, ratio, and root tests — the heart of BC series.

    10 2
  4. Ch 4

    Alternating Series & Absolute / Conditional Convergence

    AST, error bound, classification

    The Alternating Series Test, the absolute-vs-conditional distinction, and the AST error bound SSNbN+1|S - S_N| \le b_{N+1}.

    6 2
  5. Ch 5

    Power Series & Radius / Interval of Convergence

    Ratio test for R; endpoint analysis

    Find R using the ratio test, then test endpoints individually to nail down the interval — closed or open at each side.

    7 2
  6. Ch 6

    Taylor & Maclaurin Series

    Coefficients cn=f(n)(a)/n!c_n = f^{(n)}(a)/n!

    Derive the coefficient formula and write the three classics: exe^x, sinx\sin x, cosx\cos x.

    6 2
  7. Ch 7

    Common Maclaurin Expansions & Operations

    5 base series + substitution / diff / int / algebra

    Five must-memorize base series; substitution, differentiation, integration, algebra; computing limits with series.

    7 2
  8. Ch 8

    Lagrange Error Bound

    RnM(n+1)!xan+1|R_n| \le \frac{M}{(n+1)!}|x-a|^{n+1}

    The Lagrange remainder formula, the 3-step method, and the inverse "smallest degree" problem.

    7 2

Problem set (85 problems with full solutions)

Open the problem set