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Quadratic Simultaneous Equation

  • Thread starter fonz
  • Start date
  • #1
142
5

Homework Statement


Solve the equation for x

[itex]y^2 = 4x[/itex]

[itex]x^2 = 4y[/itex]

Homework Equations



None

The Attempt at a Solution



[itex]y^2 -4x = x^2 - 4y = 0[/itex]

I have spent ages re-arranging and substituting in values but I just cannot solve this thing.
 

Answers and Replies

  • #2
CAF123
Gold Member
2,895
88
Why don't you try to rearrange the second equation for y and sub into the first equation. This will give you an equation entirely in terms of x.
 
  • #3
142
5
[itex]y = 2\sqrt{x}[/itex]
[itex]y = \frac{x^{2}}{4}[/itex]

I still have no idea how to find [itex]x[/itex]
 
  • #4
33,264
4,964
[itex]y = 2\sqrt{x}[/itex]
[itex]y = \frac{x^{2}}{4}[/itex]

I still have no idea how to find [itex]x[/itex]
You didn't do what CAF123 suggested, which was to solve for y in the second equation, and then substitute for y in the first equation.

You solved for y in the second equation, but then solved for y (incorrectly) in the first equation. Note that if y2 = 4x, then y = 2√x is only one of two solutions.
 

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