Number Patterns
We investigate number sequences where consecutive terms differ by the same constant amount (linear patterns). We find the general term of such a sequence and use it to calculate any term or find the position of a given value.
12.1 Linear Number Patterns
- Investigate number patterns with a constant difference between consecutive terms
- Determine the general term of a linear pattern (without using a formula — derive it from first principles)
- Use the general term to calculate specific terms and find the position of a given term
Real-World Connection
A taxi charges R8 per kilometre. After 1 km: R8; after 2 km: R16; after 3 km: R24. The differences are all R8 — this is a linear pattern. The general term T_n = 8n lets you instantly calculate the fare for any distance without listing all the values.
Definition
Constant Difference (Linear Pattern)
A number sequence has a constant (first) difference if each term is obtained by adding the same fixed value d to the previous term. The sequence increases if d > 0 and decreases if d < 0.
Property / Rule
General Term of a Linear Pattern
For a linear pattern with first term T₁ and constant difference d, the general term (n-th term) is derived by observing how each term is built from T₁ and d. The pattern adds d exactly (n−1) times to reach the n-th term.
💡 Tip
Always verify your general term by testing it for n = 1, n = 2, and n = 3. The formula should reproduce the given terms exactly. When asked to find the POSITION of a term, set Tₙ = given value and solve for n — the answer must be a positive integer.
ℹ️ Note
The general term Tₙ = T₁ + (n−1)d can be simplified to Tₙ = an + b form (where a = d and b = T₁ − d). Both forms are correct. The ATP requires you to derive the formula rather than simply quote it.
Worked Example
Find the general term from the pattern
Problem
Worked Example
Find which term has a given value
Problem
Worked Example
Decreasing linear pattern
Problem
CAPS Cognitive Level Distribution