# How to write a vector as a linear combination

It's some combination of a sum of the vectors, so v1 plus v2 plus all the way to vn, but you scale them by arbitrary constants. We're going to do it in yellow. So if I were to write the span of a set of vectors, v1, v2, all the way to vn, that just means the set of all of the vectors, where I have c1 times v1 plus c2 times v2 all the way to cn-- let me scroll over-- all the way to cn vn.

But you can clearly represent any angle, or any vector, in R2, by these two vectors. So let's just say I define the vector a to be equal to 1, 2. Oh, it's way up there. So this was my vector a. That's all a linear combination is. I'll never get to this. I just can't do it. Maybe we can think about it visually, and then maybe we can think about it mathematically. Over here, when I had 3c2 is equal to x2 minus 2x1, I got rid of this 2 over here. And then we also know that 2 times c sorry. They're in some dimension of real space, I guess you could call it, but the idea is fairly simple.

You get this vector right here, 3, 0. Why do you have to add that little linear prefix there? If we want a point here, we just take a little smaller a, and then we can add all the b's that fill up all of that line. Let's figure it out. You can kind of view it as the space of all of the vectors that can be represented by a combination of these vectors right there.

So this is i, that's the vector i, and then the vector j is the unit vector 0, 1. Let me show you what that means. So vector b looks like that: And the fact that they're orthogonal makes them extra nice, and that's why these form-- and I'm going to throw out a word here that I haven't defined yet.

So the span of the 0 vector is just the 0 vector. All I'm saying is that look, I can multiply each of these vectors by any value, any arbitrary value, real value, and then I can add them up.

So if you add 3a to minus 2b, we get to this vector. Well, I can scale a up and down, so I can scale a up and down to get anywhere on this line, and then I can add b anywhere to it, and b is essentially going in the same direction.

I need to be able to prove to you that I can get to any x1 and any x2 with some combination of these guys.

I'm just picking these numbers at random. Now you might say, hey Sal, why are you even introducing this idea of a linear combination? Let me write it out. This is minus 2b, all the way, in standard form, standard position, minus 2b. I can add in standard form. So what's the set of all of the vectors that I can represent by adding and subtracting these vectors? So it's just c times a, all of those vectors. In most cases the value is emphasized, like in the assertion "the set of all linear combinations of v1, I made a slight error here, and this was good that I actually tried it out with real numbers.

It'll be a vector with the same slope as either a or b, or same inclination, whatever you want to call it. Please help to improve this section by introducing more precise citations.Express a vector as a linear combination of given three vectors.

Midterm exam problem and solution of linear algebra (Math ) at the Ohio State University. Problems in Mathematics. The solution is given in the post Express a Vector as a Linear Combination of Other Vectors [ ] Leave a Reply Cancel reply Your email address will not be published.

Linear Combinations of Vectors – The Basics In linear algebra, we define the concept of linear combinations in terms of vectors. But, it is actually possible to talk about linear combinations of anything as long as you understand the main idea of a linear combination.

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The Ohio State University linear algebra midterm exam problem and its solution is given. Express a vector as a linear combination of other three vectors.

In mathematics, a linear combination is an expression constructed from a set of terms by multiplying each term by a constant and adding the results (e.g. a linear combination of x and y would be any expression of the form ax + by, where a and b are constants).

How to write a vector as a linear combination
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