00:01
Given a polynomial, and i'm told it has a zero at x equals five.
00:06
So that means when i plug five in for x, i'm going to get out zero.
00:20
So let's clean this up.
00:23
5 to the fourth is 625, so this is 625a.
00:32
5 cubed is 125 times 3.
00:38
It's going to be minus 375.
00:44
25 times 63, that is minus 1575 plus 152 times 5 minus b.
00:57
And that's equal to zero.
01:02
Let's combine these constants.
01:05
I'm going to get minus 1190 minus b.
01:14
So 1190 equals 625a.
01:20
Minus b that's one equation now i'm going to use my point negative 2 negative 560 i'm going to get a second equation so that's 16 a and that will be plus 24 then four times 63 that's minus 252 minus 304 minus b.
02:16
So that's 16a, 24 minus 252 minus 304 is minus 532 minus b.
02:31
Add 532 to both sides.
02:39
That is going to give me 28 equals 16a minus b.
02:44
I'm going to combine these equations.
02:48
So i'm going to multiply by a negative 1.
02:55
That's minus, so that's plus.
02:58
That'll be minus 16a plus b.
03:03
So 625 minus 16 is 609a equal to 1190 plus 28, 1218, divide both sides by 609.
03:27
You're going to get a is 2.
03:32
Now i'm going to go back and use my equation.
03:36
1190 equals 625 times 2 minus b.
03:45
So that's 1190 equals 1250 minus b.
03:54
Subtract 1250 from both sides.
03:57
I'm going to get negative 60 is negative b, so b is positive 60.
04:07
So that's your a work.
04:12
There's your a and your b.
04:14
Use the given information to state a factor.
04:18
Well, if x equals 5 is a 0, then x minus 5 is a factor.
04:32
Now we want to find the other factors.
04:36
So let's put in our a and our b.
04:40
I have 2x to the 4th, minus 3x cubed, minus 63x squared, plus 152x, and that's going to be minus b, so minus 60.
04:58
So i know i'm going to have four zeros.
05:01
I have one already.
05:03
I have five.
05:06
I can use rational root theorem and see that f of 2 is zero.
05:12
You know f of 5 is zero.
05:27
Negative six is zero.
05:57
So it looks like one of these could be a double root unless i'm missing something.
06:10
Plugging in.
06:11
I don't think i am.
06:22
Okay, so we're going to need to use some synthetic division.
06:26
Let's just make some room here.
06:29
I'm going to start with my 5 -0...