GeoGebra Klaslokaal

# combine graphs and equations

## images of graphs

We want to combine the graphs of 4 functions with their equation. First we have to do some preparational work creating the images of the graphs. You can export the Graphics View as a picture (see the manual). Read the article in the manual and save the picture of the four following functions on your computer:
• f(x) = x²
• f(x) = x² + 2
• f(x) = (x + 2)²
• f(x) = -x²
In the manual﻿ you can read how to insert pictures in an applet.

## drop-down lists

To match the graphs with their equation we can use drop-down lists in which we can select the appropriate answer out of the options A, B, C or D and showing a blank answer as its initial position.
• Type the command list1= {"", "A", "B", "C", "D"}
• Rightclick on the list in the Algebra View to open its Properties.
• Select the tab Basic, check the option Draw as drop-down list and type graph as its Caption.
• Define ans1= SelectedIndex[list1]. When you select the option A ans will be equal to 2. At its initial position (a blank answer) ans1 will be equal to 1.

## Construction Steps

 ﻿1-12 ﻿ ﻿Select the Picture Tool and insert the pictures of the four graphs. Align them in the Graphics by dragging the defining corners. Hide these defining corner points afterwards. ﻿13-16 ﻿ ﻿Select the Text Tool and mark the graphs as A, B, C and D. ﻿17-20 ﻿ ﻿﻿Select the Text Tool and type the four equations of the functions. ﻿21-24 ﻿ ﻿Define the four lists and draw them as drop-down lists behind the equations. Attention: Make sure list1 is situated behind f1 etc. ﻿25-28 ﻿ Define the fours answers as: ans1 = SelectedIndex[list1] etc. ﻿29 ﻿ ﻿Select the Button Tool and create a button with Caption reset and scripting commands SetValue[list1,1] to reset all four drop-down lists to their initial blank position SetValue[list2,1] SetValue[list3,1] SetValue[list4,1]

## dynamic colors of the drop-down lists

Again we can use dynamic colors to control the selected answers.
• f1 = x² matches with graph D.
• The list colors red if the selection is wrong. That's if it isn't blank (ans 1) and neither D (ans 5).
• The list colors green if the selection is correct. That's if D is selected (ans = 5).
The other lists are colored similarly.

## Similar exercises

Numerous exercises can be made in a similar way combining slopes, signs, equations, derivates, graphs, a list of its roots or asymptotes, axes of symmetry...