thejoshfish
Solve the following system.
4x^2 + 9y^2 =72
x^2 - y^2 = 5
The solutions are?
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thejoshfish
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i've tried to do this at least 5 times. i don't understand it at all
mathslover
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|dw:1337656235090:dw|
mathslover
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|dw:1337656263685:dw|
mathslover
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|dw:1337656308816:dw|
Outkast3r09
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or multiply the second equation by -4
mathslover
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|dw:1337656338440:dw|
mathslover
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|dw:1337656365038:dw|
mathslover
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|dw:1337656398578:dw|
Outkast3r09
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\[4x^2+9y^2=72\]
\[-4(x^2-y^2)=-4(5)\]
mathslover
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|dw:1337656433069:dw|
thejoshfish
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there's supposed to be 2 solutions:
The solutions are:
(_,_) & (_,_)
Outkast3r09
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\[4x^2+9y^2=72\]
\[-4x^2+4y^2=-20\]
add them together to get
\[13y^2=52\]
thejoshfish
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trust me, i've gotten all the solutions possible. but the answer is still wrong.
Outkast3r09
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\[y^2=\sqrt{\frac{52}{13}}\]
mathslover
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the solutions are : sqrt(52/11) and sqrt(107/11)
thejoshfish
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but there's 4 solutions.
mathslover
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@ outkast i think y = sqrt(52/11) u wrote y^2 = sqrt(52/13) ?
Outkast3r09
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yeah i think there might be aproblem with your's mine is correct i thinkkk let me check
Outkast3r09
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yeah mine is correct .. by elimination
mathslover
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u can write it as : |dw:1337656633671:dw|
radar
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\[y=\pm2\]\[x=\pm3\]
thejoshfish
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i also got that ^
Outkast3r09
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i'ma cheat *grabs calculator
thejoshfish
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lol, i've done that too! ^
Outkast3r09
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ahh wait mathslover you have 7 instead of 9
mathslover
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hey sorry , i took 4x^2 + 7y^2 but it is 4x^2 + 9y^2 , therefore the 4 solutions are : |dw:1337656820684:dw|
Outkast3r09
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i believe you made a 9 really badly and thought it was a 7
the first equation is
4x^2+9y^2=72
brinethery
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For y, I got y= +/- sqrt (52/13)
Outkast3r09
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thats right now for x
mathslover
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yes sorry , y = + 2 , -2
x = +3 , -3
mathslover
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@Outkast3r09 x = +3 , -3 right ?
Outkast3r09
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\[x^2-(2^2)=5\]
\[x^2-(-2^2)=5\]
brinethery
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x = +/- 3
Outkast3r09
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\[x^2-4=5\]
\[x^2-4=5\]
radar
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\[\sqrt{52/13}=\pm2\]\[x ^{2}=9\]\[x=\pm3\]
brinethery
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I was slow, I was using a crappy calculator.
Outkast3r09
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does this mean it's a multiplicity of 2?
brinethery
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@thejoshfish did you try putting in y= +/- sqrt (52/13) and x=+/- 3?
brinethery
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@Outkast3r09 it means 3*3 and (-3)(-3).
thejoshfish
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i sure did. haha trust me, i tried everything. i'm so fed up.
but you guys are wonderful.
Outkast3r09
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those are your answers are you using like owl or whatever
thejoshfish
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owl?
brinethery
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Talk with your instructor. I'm taking statics and have the instructor's manual. They're wrong way more times than I'd like them to be. I think the grad students who write the manuals aren't getting enough sleep.
Outkast3r09
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Online web learning
Outkast3r09
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what does it say the answers are josh?
thejoshfish
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alpha omega academy
thejoshfish
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it doesn't tell me. but thanks for helping.
Outkast3r09
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sometimes those sites have like a function button with like +- and what not . that could be the problem
or try 3,-3 , -2 ,2
brinethery
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If you have to take the higher level physics series, they might make you use MasteringPhysics. Have fun with that! Groans.