Charas-Project
Off-Topic => All of all! => Topic started by: aboutasoandthis on October 10, 2006, 09:32:16 PM
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Can somebody help me with these?
For the most part, I'm getting the hang of these but I keep getting fractions on these two problems. I don't think I'm supposed to...at least that's what the teacher said.
6.)
2x+y-z=-8
4x-y+2z=-3
-3x+y+2z+5
I keep getting x=-42/33 for some reason.
7.)
2x-5y+z=3
3x+2y-z=17
4x-3y+2z=17
I got x=176/35.
I'm doing something wrong. I just don't know what.
EDIT=
I managed to get the first one I think. I came up with
(-2,-3,1)
If you did it, did you get that answer?
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....ROFL. A forum? Come on, seriously, a forum?
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17 views and nothing. Yet another set not done.
Where else was I gonna go? A psychic hotline? :p
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Try googling for like.. algebra problem solver
I'm sure there is one.
Yeah, but living people don't care about your homework.
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Except for Smo's. He posted em that one time. It was like 5. They all got done.
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Damn, my math class is doing ordered triples too, but I think you're one day or so ahead of me. @_@ Sorry I can't help. :(
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Smo doesn't sux.
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Well do you atleast know how to do them?
If that is what I think it is, solve one of the three first. It should always be the easiest.
By the way what math course is this, because I think i remembered doing something like this but it has bee na while so i may be wrong. Also is there anything else to the problem?
So for the first probelm use the solve 4x-y+2z=-3 for y,which is 3+4x+2z then input that answer into another equation for y.
So put it in 2x+y-z=-8 and it should look like this 2x+(3+4x+2z)-z=-8.
Which becomes 6x+z=-5. Then move 6x to the opposite side and it will be z=-6x-5.
Now these answers (((( y=3+4x+2z ,z=-6x-5)))) into the final equation and solve for X.
I think that is how you start it........i think. Like i said it has been sometime since I did any of those problems. I haven't used any of that **** in Pre-Calc yet so sorry i can't be of much more help. i think I just confused you more.
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I may sound a bit condescending, but bear with me - that's what happens when you see stuff you haven't done in years. :P
2x+y-z=-8
4x-y+2z=-3
-3x+y+2z+5
Ordered triples are used to teach you the concept of using multiple formulas to solve for a single variable - in physics, for example, sometimes you are not given a value, such as acceleration, that is needed to find another value, such as velocity (In certain cases, at least.).
The idea is that you solve one of the equations for one of the variables that you don't need to solve for, and plug it into the next one. For example, let's start with the one on the bottom.
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-3x+y+2z=5
(I'm assuming that last plus is supposed to be an equals.) Let's try solving that for z.
2z = 5 + 3x - y
(Moved both values over and switched their signs.)
z = (5 + 3x - y)/2
(Divided by two on both sides to cancel it out on the left.)
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Now we have z in terms of x and y. Now let's move to equation 2. This is where it gets a bit messy.
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4x-y+2z=-3
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First, substitute what we got for z in so that you only have TWO variables. (I'm not sure if you know this, but Order of Operations says you do everything within parenthesis first - treat them as grouping stuff.)
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4x - y + (2 * (5 + 3x - y)/2)) = -3
4x - y + 5 + 3x - y = -3
(The two multiplying the fraction cancels out with the two dividing it - making it much simpler.)
7x - 2y + 5 = -3
(Combining like terms: 4x + 3x = 7x)
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Now we only have two variables. We are trying to solve for x, so let's find y in terms of x.
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-2y = -7x - 8
(Moved over.)
y = (7x+8)/2
(Dividing by a negative reverses the signs, and I don't feel like working with fractions right now. We can do that later if it comes to it.)
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Now let's haul out the first equation. This time, we'll replace y with the equation above and z with the equation we found first - remember to replace the y WITHIN the z equation with the same formula we found above - that way the only term we have is x, meaning we can actually solve it.
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2x+y-z=-8
(I saved this one for last because it is the most simple of the three equations)
2x + ({7x+8}/2) - ({5 + 3x - ({7x+8}/2)}/2)
(A doozy of an equation. I mixed brackets to make it more readable. Alright, time to solve.)
4x + (7x+8) - (5 + 3x - {(7x+8)/2}) = -16
(I multiplied both sides by two in order to get rid of the pesky division. I can't do this twice because then I'd have to distribute it and... okay, so I can, and it would be better. Alright then.)
8x + (14x+16) - (10 + 6x - (7x+8)) = -32
(That looks way better. Since it's all addition and subtraction, we can remove the brackets and combine like terms.)
8x + 14x + 16 - 10 - 6x + 7x + 8 = -32
(Notice that I distributed the negative over the last bracketed part so that the first two are minused but the third two terms are doublenegative, meaning they're positive.)
23x + 14 = -32
(Much better. Normal solving).
23x = -46
x = -2
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There you go. Tedious, but if you know the right tricks, and try to avoid fractions AT ALL COSTS, you'll do fine.
EDIT: Oh, you have to find all of them? Well then just plug what we got for x into the equations we got before (y = (7x+8)/2 and z = (5 + 3x - y)/2, once you have the y).
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You're a saint Osmose.
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Osmose pretty much said what I said, but more clear and concise. I think I learned that stuff last year or maybe two years ago, who knows. But what Osmose has is pretty much the same. I may have messed up a tad due to not really wanteing to do math since I have to do my Pre-Calc stuff now.
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I have an easier method, but I couldn't quite figure out why I was getting fractions. I think it was bad addition or something.
I used the elimination way. You know
2x-5y+z=5 (You were right. My bad.)
3x+2y-z=17
Add the two equations together to get
5x-3y=22
Then start solving for the single variables. But with the negatives and the moving stuff around, I get confused.
But now that I have the x I'm off to a decent start.
BTW, if you're wondering, I'm taking Advanced Algebra. It's not an honors class or anything. They say it just moves a bit faster than normal.
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Gah, I'm doing all this crap in physics class right now like Osmose was talking about.
We've spend two weeks working on this. We get like a new worksheet every day or two, they're never corrected, and its just boring as hell because its not really that hard, but its taking 20 minutes to do a problem because there are 4 things each problem is asking for and it just sucks.
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You in honors? If not, is it hard?
I mean, we're doing a lot of bookwork but we haven't gotten too far into it. We're mostly doing velocity, displacement, acceleration, stuff like that.
Matter of Fact, if you do your homework, which is the one you hate doing the least?
I like Spanish, but I hate the homework. I can't translate fast enough. When you're in 4th year Spanish as a Junior, I'm not allowed to go to tutoring. :(
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Every school is different. For example, at my school, the only difference between my AP Physics and Physics honors is that AP isn't allowed to reference formulas during tests.
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YEAH!! I ask Charas for help on anything...school related..
Originally posted by Osmose
Every school is different. For example, at my school, the only difference between my AP Physics and Physics honors is that AP isn't allowed to reference formulas during tests.
Word..
I so hate math.
I understand it but, math to me is like that cousin that's really hot but you can't touch her because you're first cousins and...yeah..
(I kid...OR DO I???)
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Its really a shame that I never did any of the home work. I'm still in algebra because of the laziness XD