Hello! I’m trying to make an activity where the students will eventually create the equation for a line that connects the ends of two other lines (horizontal/vertical lines) creating a right triangle. Step 1 is figuring out what the slope of that line would be. Because I want them to think past specific numbers, I have the graph set to having lines fluctuating in size. My hope was to have a line appear with the slope they give so they could see that line move too, but when students enter values “a” and “b” (defined by the graph), it doesn’t work. It does work for numbers. Is there a way to make it do what I want?

Here’s the activity: