00:01
A picture of a function f, and here's a point x.
00:05
Then i moved over h this way to x plus h, and h this way to x minus h.
00:11
And what i want to know is the slope of the line joining these two points, called the seekin line.
00:18
Okay, well, this point would be x minus h, f of x minus h, and this point would be x plus h, f of x plus h.
00:30
So the slope would be m equals y2 minus y1 over x2 minus x1, f of x plus h minus f of x minus h over x plus h minus f of x minus h over x plus h minus f of x minus h over x plus h.
01:17
So f of x plus h minus f of x minus h over 2 h.
01:26
Okay, now it says also show that that equals the average between the slopes of these two lines.
01:35
The one that goes from x minus h to x, this one, and then the one that goes from x to x plus h.
01:46
Okay, so there's points named x, f of x.
01:50
So we'll call m1, the one that comes from here to there...