x 3 x + 3 = 8 Come play with numbers!
Patterns & next terms

Can one formula find the 10th term instantly?

# The nth term (starter) If each term adds the same number `d`, it is an **arithmetic** pattern. nth term (starter version): `first term + (n − 1) × step` Example: 5, 8, 11, 14… First = 5, step = 3 nth term = `5 + (n − 1)×3 = 3n + 2` Check: n=1 → 3+2=5 ✓ · n=2 → 6+2=8 ✓ ## You do not need the name “arithmetic sequence” in Class 6 to use this. You only need: *start, step, position.* Next stop after this path: more equations, and later graphs. You already have the core idea — **letters hold numbers, and = is a balance.** ## Start, step, seat You only need three words: - **Start** — the first term - **Step** — what you add each time - **Seat** — n, the position ``` term(n) = start + (n − 1) × step ``` Why n − 1? From your own seat back to the first seat there are n − 1 jumps, not n. ### Check pair (never skip) - n = 1 must return the start - n = 2 must return start + step If either fails, the algebra of tidying start + (n−1)d went wrong. Redo that line. ### You already own the whole starter path Letters hold numbers. Equals is a balance. Substitution checks truth. The nth term is those three ideas wearing a sequence costume.

By the end of this lesson

Write a starter nth-term for an add-the-same sequence: first + (n−1)×step, and check it on n=1 and n=2.

Remember

  • If each jump adds the same d, it is an arithmetic pattern.
  • nth term (starter): first + (n − 1) × step.
  • 5, 8, 11, 14… first=5, step=3 → 5 + (n−1)×3 = 3n + 2.
  • Always check n=1 (must give the first term) and n=2 (must give the second).
  • The point of an nth term is to jump to the 10th or 100th term without listing.

Worked examples

Cover the answer. Try the steps on paper, then open them.

Example 1 — Build 3n + 2

5, 8, 11, 14…

  1. first = 5, step = 8−5 = 3
  2. nth = 5 + (n−1)×3
  3. 5 + 3n − 3 = 3n + 2
  4. n=1 → 5 ✓ n=2 → 8 ✓

Answer: 3n + 2

Check: 10th term: 3(10)+2 = 32, no listing needed.

Example 2 — Another

2, 6, 10, 14…

  1. first=2, step=4
  2. 2 + (n−1)×4 = 4n − 2
  3. n=1 → 2 ✓ n=2 → 6 ✓

Answer: 4n − 2

Check: n=3 → 10 ✓.

Example 3 — Use it

For 3n + 2 find the 1st, 2nd and 10th terms.

  1. n=1 → 5
  2. n=2 → 8
  3. n=10 → 32

Answer: 5, 8, 32

Check: Plug n in. That is substitution again.

Common mistakes

Slip Using n instead of (n−1) steps from the first term and forgetting to check n=1.

Fix If n=1 does not give the first term, the formula is wrong.

Always test n=1.

Slip Step taken as the first term.

Fix Step is the jump: 8−5=3, not 5.

Subtract two neighbours.

Slip Listing 10 terms when you already have 3n+2.

Fix Plug n=10.

That is why the formula exists.

Try on paper first

Write the answer, then tap Reveal. These are not the quiz — they are warm-ups.

1. Step in 4, 9, 14, 19?

Answer: 5

2. nth term of 4, 9, 14, 19 (use 4+(n−1)×5).

Answer: 5n − 1

3. If nth term is 2n + 1, the 5th term is…

Answer: 11

4. If nth term is 2n + 1, the 1st term is…

Answer: 3

Touch practice

9 tap / type

Tap an option or type the answer. Retry any miss. Extra generated questions appear after the set if this topic allows it.

Optional picture lab

After practice

Real world

Predict the next bill or score.

Connect

Functions: input n, output term.

⭐ Star quiz

9 questions

Finish the touch practice first if you can. Then answer without peeking. Read every “why”.