# How to write a vector as a linear combination

This is just 0. It's like, OK, can any two vectors represent anything in R2? Wherever we want to go, we could go arbitrarily-- we could scale a up by some arbitrary value. And all a linear combination of vectors are, they're just a linear combination.

Now why do we just call them combinations?

But what is the set of all of the vectors I could've created by taking linear combinations of a and b? I can keep putting in a bunch of random real numbers here and here, and I'll just get a bunch of different linear combinations of my vectors a and b. To see that this is so, take an arbitrary vector a1,a2,a3 in R3, and write: The subtle difference between these uses is the essence of the notion of linear dependence: These form a basis for R2.

In that case, we often speak of a linear combination of the vectors v1, Please help to improve this section by introducing more precise citations.

So let me draw a and b here. It'll be a vector with the same slope as either a or b, or same inclination, whatever you want to call it. In fact, you can represent anything in R2 by these two vectors.

Let's say that they're all in Rn. And in our notation, i, the unit vector i that you learned in physics class, would be the vector 1, 0. Let's ignore c for a little bit. My a vector looked like that. I just showed you two vectors that can't represent that.

Now, if I can show you that I can always find c1's and c2's given any x1's and x2's, then I've proven that I can get to any point in R2 using just these two vectors.

You get 3c2 is equal to x2 minus 2x1. We're not multiplying the vectors times each other. And you learned that they're orthogonal, and we're going to talk a lot more about what orthogonality means, but in our traditional sense that we learned in high school, it means that they're 90 degrees.

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. And so our new vector that we would find would be something like this. Now my claim was that I can represent any point.

And then we also know that 2 times c sorry. So we get minus 2, c I'm just multiplying this times minus 2. If I were to ask just what the span of a is, it's all the vectors you can get by creating a linear combination of just a. 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.

So you give me any point in R these are just two real numbers-- and I can just perform this operation, and I'll tell you what weights to apply to a and b to get to that point.

So let's say that my combination, I say c1 times a plus c2 times b has to be equal to my vector x. And we saw in the video where I parametrized or showed a parametric representation of a line, that this, the span of just this vector a, is the line that's formed when you just scale a up and down.

However, one could also say "two different linear combinations can have the same value" in which case the expression must have been meant. So this vector is 3a, and then we added to that 2b, right? This is a linear combination of a and b.

Now, the two vectors that you're most familiar with to that span R2 are, if you take a little physics class, you have your i and j unit vectors.

However, one could also say "two different linear combinations can have the same value" in which case the expression must have been meant. So this is a set of vectors because I can pick my ci's to be any member of the real numbers, and that's true for i-- so I should write for i to be anywhere between 1 and n.

So it's just c times a, all of those 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). The concept of linear combinations is central to linear algebra and related fields of. 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. 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). 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. Question: Write each vector as a linear combination of the vectors in S.

(Use s1 and s2, respectively, for Write each vector as a linear combination of the vectors in S. (Use s 1 and s 2, respectively, for the vectors in the set%(1).

Write vector u = $$\left[\begin{array}{ccc|c}2 \\10 \\1\end{array}\right]$$ as a linear combination of the vectors in S. Use elementary row operations on an augmented matrix to find the necessary coefficients.

How to write a vector as a linear combination
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