There is an error in the Bézier curve demo on page 217 of our book Mathematics for Year 12: Specialist Mathematics. In most cases, the equations reported by this demo are incorrect (in particular, the coefficients of x3 are not calculated correctly).
If you would like to download a corrected version of this demo, please click on the link below.
Windows: Bezier.exe
Macintosh: Bezier.dmg