00:02
Hello, this is problem 3.
00:07
So our reference equation is dyd is equal to 0 .4y minus 0 .01y squared minus 0 .002 xy and we could write this as 0 .4y times 1 minus 1 minus 0 .002 xy.
00:27
And we could write this as 0 .4y times 1 minus y minus 0 .8x divided by 400 and this is called the logistic model okay now dx could be written as 0 .5 x times 1 minus x minus 0 .25 y divided by by 125 and this type of model is called the competition because when they interact it decreases how the y species is changing and is the same thing for the x species.
01:47
Okay so now to find the equilibrium we could when to 4.
01:56
We could do x is equal to 0.
02:00
So that means that the x species is dead.
02:05
And then we could let, so we know that.
02:09
So x species is dead.
02:16
We still need to figure out what y is.
02:20
So if we do dx and t, we're going to get 0 .5 times.
02:30
0 minus 0 .0 .0 .0 .04 times 0 squared.
02:40
Both of these are 0.
02:44
Then minus 0 .001 times 0 times y.
02:50
It has to equal to 0.
02:52
So this is good.
02:55
We still haven't figured out what y is though.
02:57
So now, dyd t has to equal to 0.
03:03
4 times y and then we're gonna have one minus y minus 0 .8 times 0 divided by 400 and then what we noticed that this is 0 so remember it has to go to 0 d -t has to zero.
03:29
So that is true then in order for this to be zero, then y has equal of 400.
03:43
So that's it.
03:44
So x has to be zero and y has to equal 400 in order for there to be equilibrium.
03:55
Okay, so now we move on to part two.
04:00
So we collect y is equal to zero.
04:01
So we collect y is equal to zero.
04:03
So the y species is dead.
04:13
So we have to figure out what x is.
04:16
So we do tx and t has to equal to 0 .5x times 1 minus x minus 0 .25 times 0.
04:32
And we have to divide by 125 and this whole thing has to be zero.
04:45
So this is zero already.
04:49
So in this case, we could figure out that x has to be 125 for this whole thing to be zero.
05:03
Okay, so now we move on to.....