Use the substitution method to solve
x^2+2y^2=9
x-y+3=0
can someone show me the steps?

- anonymous

Use the substitution method to solve
x^2+2y^2=9
x-y+3=0
can someone show me the steps?

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- chestercat

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- anonymous

I have already solved this before. You've asked the same question lol, search for the old one ^_^

- anonymous

oh wait, it's different ^^" my bad.

- anonymous

yea the y^2 is throwing me off.

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## More answers

- anonymous

i came up w/ x=(-1,-3) y=(2,0) but im not sure thats right...

- anonymous

Alright, first of all, call your equations as (a) and (b).
Now, let's re-write equation (b) in terms of y and we'll get:
y = 3 + x
Substitute this equation in (a) and you'll get:
\[x^2 + 2(3+x)^2 - 9 = 0\]
\[x^2 + 2(3+x)(3+x) -9 =0\]
\[x^2 + 2x^2 + 12x + 18 -9 = 0\]
\[3x^2 + 12x -9 = 0\]
\[(3x-3)(x-9) = 0\]
so x = 1 and x =3
Plug these 2 x's in equation b and find the 2 points ^_^
give it a try now :)

- anonymous

k

- anonymous

Your points should be (1,4) and (3, 6) :)

- anonymous

DOn't you mean x = 1 and x = 9

- anonymous

lol right right! >_< thank you :)

- anonymous

wait no!

- anonymous

oh dear , I messed up again the equation should be:
(3x-3)(x-3) = 0 instead of (x-9)

- anonymous

so you have x = 1 and x = 3 ^^" sorry lol

- anonymous

plug these in equation (b) and you'll get (1,4) and (3,6) as your points :)

- anonymous

and thank you blexting :)

- anonymous

it wouldnt be (1,4) and (3,12)?

- anonymous

no ,it'll be (1,4 ) and (3,6)
I made a silly mistake in the previous last line where I have put:
(3x -3)(x-9) = 0
it should be :
(3x -3)(x-3) = 0 instead :)

- anonymous

plug x = 3 in the equation and you'll get the other point (3,6)
^_^

- anonymous

ok I see. that x-9 was throwing me off. Thans for your help!

- anonymous

np :) again, sorry for the mess ^^"

- anonymous

Wait. x^2+2x+12+18-9=0
wouldnt this simplify to 3x^2+2x+9=0 ?

- anonymous

you have negative 9

- anonymous

oh right! >_< again sorry lol

- anonymous

yo'll have negative 3 and not 9

- anonymous

Ok I think i have it.

- anonymous

awesome! :)

- anonymous

awesome indeed

- anonymous

:)

- anonymous

when i solve I keep coming up with x=(-1,-3) y=(2,0)?

- anonymous

y=2 and x=1

- anonymous

or y=0 and x=3

- anonymous

yes! excellent js! :)

- anonymous

I'll give you a star ^_^

- anonymous

truly excellent...

- anonymous

a star from me too

- anonymous

lol ^_^

- anonymous

i mean y=0 and x=-3

- anonymous

lol abigail :)

- anonymous

i know what you mean, dont wory

- anonymous

thank you for your support too ^_^

- anonymous

you know what I mean?

- anonymous

i know what i know

- anonymous

so, what did I mean?

- anonymous

I know what you know I know

- anonymous

._. ...now I don't even know what I have said

- anonymous

i know you dont know what you think you dont know

- anonymous

I don't even know what I know now x_x

- anonymous

LOL, stop my head is spinning! @_@

- anonymous

Well guys i know i appreciate the help:)

- anonymous

np js :)

- anonymous

i know it is

- anonymous

I don't even know what is what right now, but I do know that the word "know" sounds funny nowx_x

- anonymous

just say "know" 29 times out loud, and then pause for 5 sec, and say it again, and i promisse, it will sound weird

- anonymous

LOL

- anonymous

go finish your 5 $ work =P

- anonymous

finished all the orders already

- anonymous

made a fortune

- anonymous

atleast you had fun :)

- radar

This solution was very difficult to follow. I hope js14 understands the final answer is x=-3, y=0

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