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Mathematics 20 Online
OpenStudy (wcrmelissa2001):

Help please (will medal) THANK YOU!

OpenStudy (wcrmelissa2001):

\[\left| x^2-4y^2+x+3y-1 \right|+(2x-y-1)^2=0\]

OpenStudy (anonymous):

here is a website i think this is what your looking for but i dont know this stuff ...... https://www.math.ucdavis.edu/~kouba/CalcOneDIRECTORY/implicitdiffsoldirectory/

OpenStudy (qwertty123):

Do you need help solving or what?

OpenStudy (anonymous):

who are you talking to? btw i dont wanna say it in a mean way

OpenStudy (qwertty123):

your fine! @wcrmelissa2001 what you need help with?

OpenStudy (anonymous):

oh ok well ima go..

OpenStudy (wcrmelissa2001):

@NicoNeedsAlotOfHelp thanks anways! @Qwertty123 I'm not sure how to solve this question (and eyyy ur back!)

OpenStudy (wcrmelissa2001):

Everytime I expand it I end up with lot of terms and no idea how to simplify it: y^2, y, x, x^2, xy

OpenStudy (qwertty123):

I am back! Lets take a look here! :D

OpenStudy (wcrmelissa2001):

@phi

OpenStudy (phi):

what techniques do you know to tackle this type of problem ?

OpenStudy (wcrmelissa2001):

Off the top of my head it would be graphs (not sure how that can be used), expansion??

OpenStudy (phi):

both terms are either 0 or positive (assuming real numbers) the only way to get the sum of two positive numbers to be 0 is to require both to be zero.

OpenStudy (wcrmelissa2001):

yup

OpenStudy (wcrmelissa2001):

but once you remove the modulus sign, the first term can be negative too am i right?

OpenStudy (phi):

yes. I'll have to think about this one.

OpenStudy (wcrmelissa2001):

thanks :D

OpenStudy (phi):

graphing both terms (but ignoring the absolute value), we have this

OpenStudy (phi):

to solve this analytically, we start by requiring 2x-y-1= 0 from which we get y= 2x -1 using that in the second term, we have \[ x^2 -4(2x-1)^2 + x +3(2x-1) -1 = 0\] if we expand that out we get \[ -15x^2 +23x -8=0 \\ 15x^2 -23x +8 =0\] the zeros occur at \[ x= \frac{23 \pm 7}{30} \]

OpenStudy (phi):

we get x= 1 (and y = 2*1 -1 = 1) and x= 16/30 = 8/15 and the corresponding y= 1/15

OpenStudy (wcrmelissa2001):

wait sorry how would u graph it out? like what are the 2 equations

OpenStudy (phi):

we require 2x-y-1=0 --> y= 2x-1 so the solution has to lie on that line

OpenStudy (phi):

we also require x^2-4y^2 +x+3y-1 =0 that is a hyperbola, and the solution has to lie on it. so the solution has to lie on the intersection of the two curves.

OpenStudy (phi):

because we insist on the term being zero, we can ignore the absolute value operator because | 0 | = 0

OpenStudy (wcrmelissa2001):

I get it :D Except for how to get the graph from x^2-4y^2 +x+3y-1 =0. You can't exactly key that in to a graphic calculator. And there is y^2 and y terms which is hard to make into equation of y

OpenStudy (phi):

are you sure? It's a hyperbola. If your calculator does circles e..g. x^2+y^2=1 then it should do hyperbolas. Or use geogebra (free download) or wolfram

OpenStudy (wcrmelissa2001):

I'm not sure because I thnk my calculator can only do y= blah blah functions but oh well. Thank you anywawy! :D

OpenStudy (phi):

you can "complete the square" on both the x and y terms and put the equation into a more standard form http://www.purplemath.com/modules/hyperbola.htm

OpenStudy (wcrmelissa2001):

ahhhh thanks :D

OpenStudy (anonymous):

@wcrmelissa2001

OpenStudy (anonymous):

thank you

OpenStudy (anonymous):

i mean your welcome by the "thanks anyways"

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