The sum of consecutive powers of 9 is a triangular number

Here's a visual proof that [math]\sum_{k=0}^n 9^k[/math] is a triangular number for each value of [math]n \in \mathbb{N}[/math].

 

timteachesmath

 
Tipo di risorsa
Attività
Tag
exploration  proof  sequences-and-series  summation  visual 
Gruppo di riferimento (età)
15 – 18
Lingua
English (United States)
 
 
 
© 2026 International GeoGebra Institute