| Author | Comment |
talachee
Probe
Posted: 3 Nov 2007
10:06 GMT
Total Posts: 4 | Hi. I am 47 years old and trying to make it through College Algebra. My instructor allows me to use my TI-89 on my tests, but I am very new to calculators and I can't figure out how to do division of polynomial fractions on my calculator. I'm supposed to do both long division and synthetic division on my next test, but if I can learn even one, that would be great! I know this is basic stuff to you, so I'm hoping someone can tell me how to solve a problem such as this example:
(x^2+3x-40)/(x+8)
I have been working with a tutor to try to learn this by long division and by synthetic division and I'm just not going to get it before my test on Monday night. Luckly, I don't have to show my work. If I can find a way to solve these on my TI-89, I'll have it made for now. I don't know if this can even be done on the calculator or if I have to write some kind of program to help solve them. I'm more than willing to buy some kind of guide or software to help me figure this stuff out if you know of one. Any help would be greatly appreciated. Thanks so much! |
Hydraliskisback
Wraith
Posted: 3 Nov 2007
11:19 GMT
Total Posts: 583 | synthetic division is easier.
you could make a program... but i havn't been able to make one work yet. interesting.
but heres how you do it.
(ax^2+bx+c)/(x-k)
so in your problem, k would be -8, a would be 1, b would be three, and c would be four.
then do this
k......a b c
______________
bring down a (excuse the periods, the forums dont take too kindly to long spaces)
-8....1 3 -40
________________
.......1
multiply that by k and put that underneath b then add b to that number
-8......1 3 -40
..........-8
_________________
........1 -5
multiply k by that number then put that underneath c then add c to that number
-8......1 3 -40
..........-8 40
__________________
..........1 -5 0
the zero under the last number means that it divided evenly
then insert x to this:
1x-5 so:
(1x -5)(x-8) = (x^2+3x-40)
also the other thing you need to watch out is for zeroes.
like in this problem
x^3+3x+8 so that
x^3+0x^2+3x+8
the correct synthetic division listing would be
k.....1 0 3 8
_______________
and then do the math.
the calculators are tricky sometimes. unless your specific then they can screw up. and they only really work with numbers, variables are only a referance to a number you make it.
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Iff Hydralisk has posted the above, the above is stupid. |
talachee
Probe
Posted: 3 Nov 2007
11:54 GMT
Total Posts: 4 | You are so right about calculators being tricky! I'm trying my best to learn to enter problems correctly. I have been getting rather random answers so far, but I'm passing my course right now.
I would like to do better than just passing since I have a perfect GPA to this point. All I have left to take before graduating is this math and then Math 112, which is pre-cal or something. I graduate in the Spring and I'm not happy about ruining my GPA with all this math.
Seems I'm hopeless when it comes to learning this stuff, so I have been limping through by using my calculator. I failed third grade math and only made it through high school by wearing short skirts and smiling alot(all of our math teachers were men). That's not going to work for me now that I'm almost a senior citizen! I'm doing tons of extra homework in hopes of getting some extra credit to improve my GPA. If that does not work, I guess I'll try paying someone off for a few extra point. I'm going to be lucky if I manage to get through this course with a C average(which is what I have now in this class).
Anyway, I'll try my best to figure out the instructions in your post. I've never written a program, but I'm more than willing to figure out how to do it. Thank you so much for taking time to help! |
Hydraliskisback
Wraith
Posted: 3 Nov 2007
12:56 GMT
Total Posts: 583 | hmm your right i could have explained it better, but basically its like this:
k......a...b...c
___+0_+kd_+ke_
.......d..e...f
kd is k times d
and ke is k times e
soya
thats the gist of it just use that. and it extends, the higher the first exponent, the more terms used on the top.
soya.
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Iff Hydralisk has posted the above, the above is stupid. |
Barrett
Administrator
Posted: 4 Nov 2007
17:43 GMT
Total Posts: 1676 | I'm not sure if this has been mentioned, but with the TI-89, you can just type it right into the calculator, hit enter, and it will give you the answer. Just be sure to include parenthesis.
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-Barrett A |
Hydraliskisback
Wraith
Posted: 4 Nov 2007
18:21 GMT
Total Posts: 583 | amazing. i didnt know the 89 could do variables like that. D: i want one.
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Iff Hydralisk has posted the above, the above is stupid. |
Lunchbox
Carrier
Posted: 4 Nov 2007
20:24 GMT
Total Posts: 2007 | And make sure no value is stored to X when you do it, or else it will compute the value. |
Hydraliskisback
Wraith
Posted: 4 Nov 2007
20:29 GMT
Total Posts: 583 | course. so if i had an 89 i would do delvar X first, right?
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Iff Hydralisk has posted the above, the above is stupid. |
Xphoenix
Ultralisk
Posted: 4 Nov 2007
20:51 GMT
Total Posts: 210 | That, or delete through the VAR-LINK menu, or at the home screen do F6 for Clean up and enter for clear a-z. . .
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~Xphoenix |
talachee
Probe
Posted: 4 Nov 2007
21:25 GMT
Total Posts: 4 | I do have the TI-89 Titanium. I use it for all of my factoring and solving and such, but the division problems are not coming out right. The monomial problems usually work, but some of the bi or tri, the answer is wrong. I can't figure out how to work problems that have a remainder. Maybe I need to put it in exact mode instead of auto? For instance, if I input this problem exactly as written:
(x^2+3x-40)/(x+8) The answer comes out x-5, which is correct.
However, (4r^3+2r^2+10)/(2r+4) inputed into my TI-89 comes out
(2r^3+r^2+5)over(r+2). The correct answer should have been (2r^2-3r+6)Reminder -14.
Maybe it's some little simple thing that I am doing wrong and you guys can spot it for me? My test is Monday night at 6:00 pm, so I'll be trying to figure it out until then. I sure hope he does not have many of these on the test!
How do I make sure that no variable is stored to x?
Thanks again for all the help! |
talachee
Probe
Posted: 4 Nov 2007
21:34 GMT
Total Posts: 4 | Xphoenix, I tried the F-6 cleanup from the homescreen(I actually went to the calculator icon and then to F6 under that screen, so if that's wrong let me know)and I got a different answer. However, it is still not an answer with a remainder.
It would really help if I knew something about math because I'm sure that you can probably look at the answer and see how to find the remainder, but I can't.
(4r^3+2r^2+10)/(2r+4) gave me (2r^3+r^2+5)over(r+2) when the correct answer is(2r^2-3r+6)Reminder -14. Any suggestions about how I might enter this differently to come up with the correct answer? Thanks.
|
Hydraliskisback
Wraith
Posted: 5 Nov 2007
15:46 GMT
Total Posts: 583 | when it says remainder, be sure to write that down on your paper as -14 /(r+2)
because tahts how remainders are in this case.
lemme see how this works out
4r^3+2r^2+10/2r+4
k=-4
-4|......4.....2....10
......................
______________________
......................
-4|......4.....2....10
.........0...4*-4.....
______________________
.........4............
-4|......4.....2....10
.........0....-16...14*4
______________________
.........4....-14.....
-4|......4.....2....10
.........0....-16...56
______________________
.........4....-14...66
4x-14+((66)/(2r+2))
hmmm interesting outcome. anyone else see some sort of problem?
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Iff Hydralisk has posted the above, the above is stupid. |
Xphoenix
Ultralisk
Posted: 5 Nov 2007
18:23 GMT
Total Posts: 210 | I put an expand(), which you can find in the Algebra menu ([F2]), around that expression, and got:
(-7/r+2)+2r^2-3r+6
Test with expand() and see what happens.
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~Xphoenix |
gulyman
Goliath
Posted: 14 Nov 2007
18:19 GMT
Total Posts: 144 | In the problem above you didn't put in place holders. Does the calculator do that automaticaly?
It has to do with the degree of the function. Your degree is the highest exponent of any of your x's. If you have 5x^3+2x^4+x+14 then you have a degree of 4. To get the above function ready for division you need to rearange the different parts of the polynomial. Because it has a forth degree, it needs to be written in this format
ax^4+bx^3+cx^2+dx+e
since the above polynomial has 0 for the coeficient of x^2 , x^2 isn't in the polynomial. But you still need to put somthing in the place of c so you put a zero. So in your synthetic division you need to have 0 as the third number. I'm dividing this by (x-2)
2 | 2 5 0 14
..|___________
@ Hydralisk: You need to put a zero between your 2 and 10 in your dividend.
I hope this is easy to understand. |
Hydraliskisback
Wraith
Posted: 14 Nov 2007
18:36 GMT
Total Posts: 583 | im sure the calc does that automatically
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Iff Hydralisk has posted the above, the above is stupid. |
