00:02
We're given a decay function.
00:05
Your amount at time t, a sub t, equals your amount at time zero, meaning your starting value, times e to the negative 0 .00043 to the t power.
00:18
What's the half -life of this? remember, a half -life is when whatever you started with, how much time it takes to have half of that.
00:27
And because we know that this is a decay function, because that, that power is a negative number.
00:36
So our amount over time is going to be decreasing.
00:40
T refers to our time in years.
00:45
A sub zero, we said.
00:46
That's our amount at time zero.
00:48
A as a function of t is our amount at time t.
00:52
So the half life is when the amount you have is half of the amount you started with.
01:02
And remember, we started with a sub zero.
01:05
So we could just rewrite this.
01:11
And our goal here is to solve for t.
01:14
So let's go ahead and get rid of that a sub -zero...