Continuing from his method.
Year 10 method. You will learn Calculus in Year 11 and find a more efficient method. For now this method will do.
Finding intercepts
![](https://latex.codecogs.com/png.latex?\bg_white x)
and
![](https://latex.codecogs.com/png.latex?\bg_white y)
intercepts.
I like
![](https://latex.codecogs.com/png.latex?\bg_white x)
better than
![](https://latex.codecogs.com/png.latex?\bg_white y)
. So we will find the
![](https://latex.codecogs.com/png.latex?\bg_white x)
intercept first.
![](https://latex.codecogs.com/png.latex?\bg_white x)
intercept: Let
Now,
Let
Plot this into your graph. Your graph should now look like this.
Now you have a dilemma. Where should you start your graph? There are two possible starting points. Top of the
![](https://latex.codecogs.com/png.latex?\bg_white x)
axis or the bottom of the
![](https://latex.codecogs.com/png.latex?\bg_white x)
axis. So how do we decide?
If we look at our equation of our graph,
If we expand it out, we get
![](https://latex.codecogs.com/png.latex?\bg_white 2x^3.....)
. Since the power of three is the highest power, we will inspect the coefficient of it. It is
![](https://latex.codecogs.com/png.latex?\bg_white 2)
. Two is a positive number. So we will start from the top.
It will start here!
Now, we will consider three possible drawings.
SMOOTH LINE![ONE DEGREE]
BOUNCE OFF (REJECTION!)[EVEN DEGREE]
HORIZONTAL INFLEXION (JINK/HUMP) [ODD DEGREE]
So let's consider the first intercept it will cross. Our closest one is 1. We can see that,
![](https://latex.codecogs.com/png.latex?\bg_white y=2x(x-1)(x+2))
was our graph.
Let's focus on
![](https://latex.codecogs.com/png.latex?\bg_white (x-1))
. It has a degree of 1. So it will be a smooth line forward.
Our next
![](https://latex.codecogs.com/png.latex?\bg_white x)
intercept is 0. Let's focus on
![](https://latex.codecogs.com/png.latex?\bg_white 2x)
. It has a degree of 1. So it will also be a smooth line.
So your graph is now like this.
Finally the
![](https://latex.codecogs.com/png.latex?\bg_white x)
intercept is -2. Let's focus on
![](https://latex.codecogs.com/png.latex?\bg_white (x+2))
. It has a degree of 1. So it will also be a smooth line.
So your graph is like this.