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Maths - simultaneous equations

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Whickerman | 16:05 Sun 08th Feb 2009 | Science
4 Answers
trying to help my daughter with her homework, and for most of the simultaneous equations she's on top of it, but this one's a stinker:
Solve for x and y:
x2+xy-4y2=2 (that's x squared and 4y squared)
2x-3y=1

Can anyone tell me how you solve this one simultaneously? Thanks in advance
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Rearrange the second equation to be in terms of x or y:

x = 0.5(1+3y)

Then substitute that into the first equation.

You should get two values of y, and two corresponding values of x.
0.25(1+6y+9yy) + 0.5(y+3yy)-4yy=2
0.25(1+6y+9yy) + 0.5(y+3yy)-4yy-2=0
1+6y+9yy+2y+6yy-16yy-8=0
-1yy+8y-7=0
1yy-8y+7=0
(y-7)(y-1)=0
y = 7 or y = 1

x = 0.5(1+3y)

if y = 7, x = 11
if y = 1, x = 2
-- answer removed --
Question Author
Spacechimp, you're a star! Thanks so much!

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