So we've worked with real numbers like three and imaginary numbers like two I separately. But you're often going to see expressions that have these two numbers together. So something like three plus two I and these are actually called complex numbers when I have both a real number and an imaginary number added together. Now, complex numbers are going to be really important for us throughout the this course and have a ton of different uses. And while they might sound a little complicated at first, I'm gonna walk you through what they are and how we use them step by step. So let's get started. So a complex number has a standard form of A plus B I. So in this complex number, A plus bi A is called the real part of the number. And B is called the imaginary part because it's multiplying I or imaginary unit. Now, it's important to know that B by itself is the imaginary part. It's not the whole term B I. So when I'm identifying the real and the imaginary part in the number I have up here, this three plus two I three is going to be the real part of my number and then two is going to be the iag part, just the two by itself. Now let's look at a couple of different examples of complex numbers and identify the real and imaginary parts of each of them. So first I have this four minus three, I, so looking at this number, the real part A is gonna be this four because it's out there by itself, it's not multiplying my imaginary unit. This is going to be my real part A then B, so I want to look for what is multiplying I my imaginary unit. And in this case, it is negative three. Now it's important to look at everything that's multiplying our imaginary unit. So if it's a negative number, if it's a square root, if it's a combination of a number and a square root, I want to get everything that's multiplying my imaginary unit. So in this case, B is going to be a negative three, that's what's multiplying my imaginary unit. I let's look at another example. So here I have zero plus seven, I now if I look for the real part of my number, what is not multiplying my imaginary unit? I have this as zero. So that means that a, my real part is going to be zero, then B my imaginary part, the part that's multiplying my imaginary unit, I, in this case is going to be positive seven. Now you might look at this number and think, couldn't you just write that number as seven I that zero isn't really doing anything. And you're right, I could just write this as seven I, but we still need to know that if we looking at this as a complex number, it still has a real part, it's just zero. So let's look at another example. So I have two plus zero I over here. So what do you think the real part of this number is? Well, since this two is out here by itself, it's not multiplying my imaginary unit two is going to be the real part of my number A then looking at B so the iag part, the part that is multiplying my imaginary unit in this case is just zero. So again, you might be looking at this number thinking, isn't that just a real number? Couldn't I just write that as two? And you're right again, I could just write this as two. But remember if we're looking at this as a complex number, it still has an imaginary part, it's just zero. So that's all for this one. And I'll see you in the next video.