Visual patterns (matchsticks)

Overview

Induce aₙ: n squares need 3n + 1 matchsticks.

Explanation

Look at the first figures, then write a formula for the nth term (or partial sum).
Here: first square uses 4 sticks; each new square adds 3.
Total = 4 + 3(n − 1) = 3n + 1.

How to use

Change n and count sticks: 4 for the first square, +3 thereafter.

Knowledge points

• Patterns
• Algebra