Exam Strategy

Readiness Check

You are ready when you can (1) classify arith vs geo from differences/ratios, (2) write both $a_0+dn$ and $a_k+d(n-k)$ forms, (3) write both $g_0 r^n$ and $g_k r^{n-k}$ forms, and (4) explain why increasing geometric steps get larger while arithmetic steps stay equal.

Prep Sequence

1. Drill classify 10 short lists. 2. Five arithmetic closed forms (including negative $d$). 3. Five geometric closed forms (including $0<r<1$ and $r<0$). 4. Two shift-form items using $a_k$ / $g_k$. 5. One contrast paragraph (2.1.B.3).

On the Exam

• Compute successive differences and ratios before writing a formula.
• Match the formula index to the problem's starting index ($a_0$ vs $a_1$).
• For geometric with negative $r$, track signs carefully.
• Sketch as dots; say "discrete."

Common Traps

• Formula with wrong reference term ($a_0$ vs $a_1$).
• Writing $g_n=g_0+r^n$.
• Treating the graph as a continuous exponential/linear curve.
• Claiming geometric increases by a constant amount.

Quick Checklist

• [ ] Classified with $d$ or $r$ evidence
• [ ] Correct closed form for the given index convention
• [ ] Term evaluation matches substitution
• [ ] Discrete graph language used when asked
• [ ] Growth-contrast correct for increasing cases