00:01
This item has multiple parts.
00:05
The first part, a, asks that we list all the possible rational roots.
00:11
We do that, let me make sure this looks like a six.
00:15
We do that by dividing all the factors of the final constant are the factors of the leading term coefficient.
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So let's go ahead.
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We'll have 1, 2, 4, and 1 -2.
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When we develop this answer a little bit further.
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We see that we have all these combinations.
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Now we're going to go ahead and come up with our final list.
00:53
We've got a positive negative 1, positive negative 2, positive negative 4.
01:01
We have 1 half.
01:03
This is also 1.
01:05
This is also 2.
01:06
So this is the final list of all of the possible rational root.
01:12
So that takes care of a.
01:18
B.
01:19
B asks you to use synthetic division to test the possible rational roots and find an actual root.
01:26
Let's start from the right on this.
01:29
Let's start with one half.
01:35
We set up the problem for synthetic division.
01:40
We drop the first value to multiply, get a 1, add negative 4.
01:47
You multiply, get a negative 2, add, get a negative 8.
01:56
Multiply, negative 4, add we got a 0.
02:01
That was pretty awesome.
02:03
We have one zero, or one root, we're referring to these as roots.
02:10
We have a root and it is one half.
02:14
Okay, let's continue with part c.
02:18
In part c, you are asked to use this quotient, use the result, to find the remaining roots and solve the equation.
02:27
So we've got 2x squared minus 4x minus 8 equals 0.
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Here we would have the task of finding the factors of negative 8 that add to negative 4.
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So let's see.
02:44
We would have positive negative 1 -8 or positive negative 4 -2.
02:51
Oh, i'm sorry, it's not even.
02:53
Look at that.
02:53
I wasn't paying attention.
02:55
Let's go back and talk about this again.
02:59
We have a coefficient here of 2.
03:02
So we would need to find the factors of negative 16 that add to negative 4.
03:08
Let's try that again.
03:10
Factors of negative 16 add to 4.
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So factors of negative 16, 1 in 16, 2 and 8, 4 and 4.
03:23
And we would need a combination that adds to negative 4.
03:27
I think as you can see here, we're not going to get that combination.
03:32
So we can't factor.
03:33
So let's go ahead and use the quadratic formula.
03:36
And just so that we have more space, i'm going to add another slide.
03:40
We'll bring this quotient.
03:43
We'll bring this equation over to the next slide.
03:47
So we've got 2x squared minus 4x minus 8.
03:59
Okay.
04:01
Let's recall that the quadratic formula is not b equals.
04:07
It is x equals negative b.
04:11
Plus or minus square root of b squared minus 4a c all over 2a let's recall that the a will be this 2 negative 4 is b and negative 8 is c so let's make our substitutions x equals the opposite of negative 4 so positive 4 plus or minus square root of negative 4 squared minus 4 times 2 times negative 8, all divided by 2 times 2 times 2.
05:03
Let's bring this work up here.
05:07
So we get that x equals 4 plus or minus square root of 16 plus, what do we've got, 6 times 8, 48, all divided by 4, 4, plus or plus or.
05:29
Or minus the square root of 4864, all over four equals four plus or minus eight divided by four.
05:44
We've got to do a negative case and the positive case here or subtraction addition, four minus eight divided by four equals negative four over four or negative one...