### Euclid's Algorithm I

How can we solve equations like 13x + 29y = 42 or 2x +4y = 13 with the solutions x and y being integers? Read this article to find out.

### Which Twin Is Older?

A simplified account of special relativity and the twins paradox.

# A Brief Introduction to the Argand Diagram

##### Age 14 to 18 Challenge Level:

Pick a point for $z_1$ such as $2+i$. Move $z_2$ around, and keep a record of the points where $z_3$ is on the x-axis. What do you notice about the coordinates of $z_2$ and $z_3$?

Repeat for some other points.