Let's imagine you have some toy cars that you want to put in a straight line from one side of the room to the other. You put the first car down, and then you want to put the second car next to it in a straight line. You can think of this as a "linear extension" - you're extending the line of cars in a straight line.
Linear extension in linear algebra is kind of like this. We start with a set of things, like numbers or vectors, and we want to extend them in a straight line. But instead of toy cars, we're working with something called a "vector space." A vector space is just a place where we can play with vectors (which are just combinations of numbers).
So let's say we have some vectors that we want to extend in a straight line. We can do this by multiplying each vector by a number (which we call a "scalar") and adding them all together. This gives us a new vector that "extends" our original set of vectors.
For example, let's say we have two vectors: (1, 2) and (3, 4). We want to extend them in a straight line. We can do this by multiplying the first vector by a scalar (let's call it "a") and the second vector by another scalar (let's call it "b"). Then we add them together:
(a * 1, a * 2) + (b * 3, b * 4) = (a * 1 + b * 3, a * 2 + b * 4)
This gives us a new vector (a * 1 + b * 3, a * 2 + b * 4) that extends our original set of vectors in a straight line.
Linear extension might seem complicated, but really it's just a way of taking a bunch of vectors and extending them in a straight line. It's kind of like putting toy cars in a line, but with numbers and vectors instead!