Students in this video, let's get started with straight lines.
All right, well, over here we have our X and Y axis.
Now, let me write an equation of a line I have for X plus three.
Y is equal to 12.
Now, this describes a straight line.
Now, what do I mean?
When I say that this describes a straight line, it means that every solution of this equation will
lie on a straight line.
For example, let's take some solutions.
I have X, I have Y over here.
Now you will see that when X is equal to zero, that's zero plus three, Y is equal to twelve.
That is why it is equal to four.
Right.
So zero four is one solution for this equation.
Similarly, when X is equal to three, you have twelve plus three.
Y is equal to twelve.
That is three.
Y is equal to zero.
Therefore Y is equal to zero three.
Zero is also a solution of this equation over here.
All right.
Now let's plot these two points.
I have zero for over here and I have three zero over here.
Now, if I join these two points.
I'll get a straight line right now when we say that this equation is a straight line, what we mean
is that you take any point on this straight line, it will satisfy this equation.
Similarly, you find any solution of this in this equation.
It will lie on this line.
So that is what we mean when we say that this equation describes a line.
Let's take another example.
What would the solution be when X is equal to one?
When X is equal to one, you get four plus three, Y is equal to twelve or three.
Y is equal to eight, or Y is equal to eight by three.
Right over here.
If you draw a line at X equal to one right, it will intersect.
This line over here at Y is equal to eight by three.
That is what we mean when we say that this describes a straight line.
Now this is one way in which we write a straight line.
This is the generic form.
And let me write the generic formula here.
That would be X plus B Y policy is equal to zero for this.
Over here is the generic form of a straight line in the X Y plain.