How to Build a Parabola
If one were to construct a yaxis and xaxis as imperfectly diagrammed by placing equidistant points along the axes and numbering them in the following way:
10_

09_

08_

07_

06_

05_
 points on the axes are to be equidistant
04_

03_

02_

01_

. . . . . . . . . . .
10 09 08 07 06 05 04 03 02 01
One can take a pine board and drive small nails equally spaced along the axes at the numbered points as shown, and then by extending straight lengths of wire to connect the 01, 02, 03... on the xaxis to its counterpart on the yaxis, (notice the reverse order on the xaxis) one may build a nice parabola.
The resulting wire lengths represent the tangents to the generated curve. If one were to increase the number of points on each axis let's say by doubling their number so that the numbers on the yaxis ran 01,02...,19,20 and those on the xaxis ran 20,19,...,02,01, and then connect them there would be more tangents and the parabola more perfectly described. Makes a suitable toy for idiots.
Four Fours
Here is something to waste some time with:
Represent every counting number from zero to twenty using four fours and any math symbol.
For example:
2 = (4 x 4)/(4 + 4)
Always use no fewer than four four's and no more.
Good Luck!