00:01
All right, we have a parabola and its span is 120.
00:04
It's max height is 25.
00:06
So the best place to put it would be like this, so that this is 25 here.
00:14
And then this would be 60 and this would be minus 60.
00:19
So then its equation is y equals minus something x squared.
00:27
Oh, no.
00:29
Minus something times x squared plus 25.
00:36
Okay, because it shifted up 25.
00:41
Okay, well, we know that when y is zero, x is 60, 30 equals minus a times 60 squared plus 25, or 60 squared a equals 25, or a is 25 over 60 squared, 25 over 3 ,600.
01:08
One and i divide first because i don't want to think about that.
01:12
5 will go on to 6012 times.
01:16
Oh, this is 5 squared.
01:18
So this is 5 over 60 squared.
01:23
So 112 squared.
01:25
So y is minus 1 over 144 x squared plus 25.
01:32
So if you plug in x equals 0, you get y is 25.
01:36
If you plug in y equals zero, you get x is 60.
01:44
Okay, so find the height at 10...