00:01
So for this problem, we are finding all of the complex solutions for the equation z cubed plus i z equals zero.
00:15
So let's start by trying to factor.
00:19
So we can factor out a z, which leaves us with z squared plus i.
00:26
And this is a start as in it only tells us that z can be zero because we have a variable times another variable that means that one of them has to be zero so we can start by saying z equals zero that is one solution.
00:52
But then our other solution is if z squared plus i equals zero.
01:01
So now we need to work on this one.
01:04
So let's start by just moving the i to the other side.
01:08
So we have z squared equals negative i.
01:14
Now this looks a little more doable because if we take the square root of both sides, that just gives us z equals negative i raise to the one -half power.
01:32
Now this looks familiar.
01:34
We can use de mova's theorem to solve this, and we know that negative i in trig form, we can write that as, so negative i equals cis, negative pi, over 2...