00:01
Using the graph above, we're going to answer a whole bunch of questions that we have.
00:05
So first is find f of zero and f of six.
00:09
So remember that this means that x is zero.
00:13
And here, this means x is six.
00:15
So what we want to do is we want to look at our x axis.
00:19
And right here, this is where x is zero.
00:22
Well, the coordinate, the y part of that is zero.
00:26
So f of zero equals zero.
00:30
Now let's look along our x -axis and we're going to see here is six.
00:35
Well, the y -cordinate when x is six is zero, so f -of -6 equals zero as well.
00:43
Now, let's take a look at the next one.
00:46
We're going to find f -of -2 and negative two.
00:48
We're going to do the same thing.
00:51
So if you look, here is where x is two, but there's no point there.
00:56
There's no graph there.
00:57
So if we go down, now we see the point, and the y coordinate is negative 2.
01:03
So when x is 2, y is negative 2.
01:09
Let's take a look at when x is negative 2.
01:12
So i'm going to go along the x -axis to negative 2, and then i have to go up and here is my ordered pair.
01:18
There is a point on the graph.
01:20
So when f of negative 2 is positive 1, because that's where the point is on the graph.
01:30
Now, let me raise some of this.
01:32
Let's take a look at f of 3.
01:35
Here's f of 3, which is between 2 and 4, and now when i go down, it's somewhere here on the graph.
01:44
It's just asking, is f of 3 positive or negative? well, since it's below the x -axis, it has to be negative.
01:54
We're not asking for the exact number.
01:56
They just want to know if it would be a negative number or positive number.
01:59
Now let's do the same thing.
02:02
If f is f of negative 1, is f of negative 1 positive or negative? so let's go over to negative 1.
02:10
And if i go up to the graph, it is above the x -axis.
02:14
So it has to be positive.
02:18
For all the values, so now we want to find all the values of x where f of x is zero.
02:25
Remember, that means where y is zero.
02:27
So if we take a look at the graph here, y is zero.
02:32
Zero along the x -axis so let's find all the values i see a point here so x is zero four and six they're all your x intercepts so when x is zero four and six now let's take a look at part f here for what values of x is f of x less than zero which means y is less than zero which means we want y to be negative numbers or sorry the x values should be that means y is negative so let's look at the graph so i'm going to draw a line all the values below the x -axis okay is where y is negative so it wanted the x values so as you could see here from zero to four not including zero to four those values will be negative.
03:46
So we can write that in interval notation...