00:01
We want to find all the real and imaginary zeros for our polynomial function here.
00:06
So the first thing that we should probably do, just so we're not guessing a ton of values, is to use the rational zero theorem.
00:13
So our constants p, our leading coefficient is q, and we are going to look at the factors of p over the factors of q, which is going to be equal to.
00:32
So the factors of p, also first let's put plus and minus on the outside.
00:38
So it would be 1 and 5, and then the factors of q are going to be 1, 2, and 4.
00:44
So these are going to be all the possible combinations that we could get.
00:49
And now, just so we're not sitting around watching me try a bunch of different values, i'm going to have some divine inspiration and try negative 1 -half.
01:00
Now i'm going to use synthetic division for this because if we have a cubic function and this divides, then we'll have a quadratic that we're left with and we can just use a quadratic formula to get our other two zeros.
01:14
So let's go ahead and do that.
01:15
So we have 4, negative 10, 4 and 5.
01:20
So we drop down the 4.
01:23
Negative 1 1⁄2 gives us negative 2.
01:27
That will give us negative 12.
01:29
Then we get 6, 10, 10, and 5...