00:01
Even if you're not very good at knowing where 4x minus x squared is on the graph, i think it's useful to consider that we're revolving around the x -axis, and we have the bounds of y equals zero.
00:19
So it makes sense to set that equation equal to zero, and i would just factor out an x, except i wrote it wrong, for minus x.
00:29
And so to me it makes sense then that they're intersecting the x -axis at zero and four when you use a zero product property.
00:36
I also know it's a downward view because it's that negative negative x squared makes it a downward view.
00:43
So we're revolving these circles this way.
00:47
That should be a wider.
00:48
They even tell you it's the disk method going from zero to four because we found the points of intersection of the function being squared dx.
00:58
So at this point, i would encourage students, you know, if you're afraid of doing this wrong, to go ahead and foil out 4x minus x squared squared...