13.
Consider the infinite geometric series 51+110+120+140+180+.
How do you graphically and algebraically explain to students what happens to Sn as n increases?

111.6.25補充
以下的圖出自
Proofs without Words: Exercises in Visual Thinking (Classroom Resource Materials) First Edition, Later Printing
https://www.amazon.com/Proofs-wi ... sroom/dp/0883857006