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NEED MATH HELP QUICK!!!!!!!! (CONICS)

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anxju
Posts: 9371 - Karma: 61
for those of you that care for karma, ill give you 10. for those of you that dont, youll get mad karma in real life. if you dont care about that either, just be nice!

ok so were doing conics in precalc, and i have a test tomorrow. i wasnt here for a few days, so i need help with these problems.

find the points of intersection and sketch:

x^2 + y^2 - 18x + 24y + 200 = 0
and
4x + 3y = 0




the second problem is:

y^2 - 2x - 10y + 31 = 0
and
x - y + 2 = 0






thanks!! could you tell me how you solved it? spare the asian comments!!
Oct 22 2008 10:30PM
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natedogg789435
Posts: 1177 - Karma: 9
graphing calculator
Oct 22 2008 10:34PM
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anxju
Posts: 9371 - Karma: 61
we cant use those, we gotta solve it algebraically
Oct 22 2008 10:35PM
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4-Front
Posts: 5306 - Karma: 199
solve for x or y in the simpler smaller equation.  Then subsititue the x or y into the big fucking nasty question.  1 equation 1 variable. You can now solve.
Oct 22 2008 10:41PM
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natedogg789435
Posts: 1177 - Karma: 9
make a table of values?
Oct 22 2008 10:44PM
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VCharette
Posts: 4276 - Karma: 1,047

here for the second one the first is the same thing

1) y^2 - 2x - 10y + 31 = 0
and
2) x - y + 2 = 0

so you change the number to make it

 x=y+2

y^2-2(y+2)-10y+31=0

y^2-2y-4-10y+31=0

y^2-12y+27=o

(y^2-3y)(-9y+27)

y(y-3)-9(y-3)

(y-3)(y-9)

y=3

y=9

hopefully thats what you were looking for tell me if u need any more help!

Oct 22 2008 10:56PM
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860
Posts: 2930 - Karma: 166
dont you just move the equation into y=mx+b form and then graph it? Putting that in y=mx+b would be a bitch though
Oct 22 2008 10:59PM
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MCIRONCOCK
Posts: 3094 - Karma: 30
So this is what i'm doing next year -_-
Oct 22 2008 11:02PM
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VCharette
Posts: 4276 - Karma: 1,047

^ oh and btw forgot to mention

you gotta replace what you got for y (3 and 9 if i remember well) and put them in the equations

x-3+2=0  x-1=0     x=1

x-9+2=0    x-7=0     x=7   

(1,3)   (7,9) is your answer yo! i think

Oct 22 2008 11:02PM
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clrumivier4life
Posts: 2429 - Karma: 9

x=y+2
You solved this wrong...
x = y - 2

y^2-2(y-2)-10y+31=0

y^2-2y-4-10y+31 = 0

y^2-12y+27 = 0

(y-3)(y-9) = 0

y = 3 and 9

solve for x

x=y-2

x=3-2=1

x=9-2=7

so your solutions are ordered pairs:

(1,3) and (7,9)
Oct 22 2008 11:05PM
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anxju
Posts: 9371 - Karma: 61
ya i solved that one, but yours is actually wrong. on the answer sheet its different. and i got the right answer

you make x - y + 2 =0 into x = y -2. because you subtract 2 from both sides, not add

thanks though

Oct 22 2008 11:06PM
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gordie.
Posts: 2014 - Karma: 84
fuck i remember doing this shit.. not well though lol
ya but doing it that way gets you the right answer, but it takes forever and you need to graph it out on paper. they probably want you to use substitution im guessing, im pretty sure someone else already said it. just simplify one of the equations (whichever one is easier) so that either x or y is alone on the left side and all the other shit is on the other side, then (if it was x= 4y-6 for example) you substitute the whole right side into the other equation, replacing any x with (4y-6), because theyre equal. keep going till you get y, then go back and put y into any of the equations and bam. you have x and y, and u use that to get you POI. i don't really remember how though exactly. so pretty much all of that was wrong. cheers.
Oct 22 2008 11:06PM
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anxju
Posts: 9371 - Karma: 61
you got it wrong too

-2 * (y-2) = -2y + 2

so its x = y-2

y^2 -2y + 4 - 10y + 31 = 0
y^2 -12y + 35 = 0
(y -5)^2 * (y-7)^2 = 0

then plug and chug


lol i post to ask for help, but im the one correcting 2 people
Oct 22 2008 11:09PM
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VCharette
Posts: 4276 - Karma: 1,047

wait im not wrong... x-y+2=0 so   x-y=-2    x=y-2 thats it no? cause i got the good answer anyways lol? need help for the other one? and how old are you?

Oct 22 2008 11:09PM
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hey_dude_its_me
Posts: 1403 - Karma: 32
make sure you pay attention to this shit, I know it seems worthless but I can't evem begin to tell you how many times I have had to use shit like this in my post-college life aahhahahahah jk
Oct 22 2008 11:13PM
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anxju
Posts: 9371 - Karma: 61
in your first response you said it was x=y + 2

yeahi would like help wiht the first one, im 16. thanks
Oct 22 2008 11:14PM
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860
Posts: 2930 - Karma: 166
ya i havn't taken economics yet so i was just throwin it out there haha
Oct 22 2008 11:16PM
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VCharette
Posts: 4276 - Karma: 1,047

wait actually im kinda lost on the second one ill try to do it on a sheet of paper and hit u back if i find it cause i always end up with no knowing what x AND y are so shit's fucked up lol

Oct 22 2008 11:20PM
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clrumivier4life
Posts: 2429 - Karma: 9
Wow. I corrected the one guy then did the same exact thing


y^2-2y-4-10y+31 = 0
Oct 23 2008 8:22AM
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TerminatorX
Posts: 3087 - Karma: 169
i never thought a would see the day where an asian would ask for help in math.
Oct 23 2008 8:52AM
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BMB
Posts: 3138 - Karma: 232
wow, Ju asking for Hw help, what a surprise, naw man i wouldve hepled u but it's too late by now im sure.
Oct 23 2008 2:35PM
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