Parabola equation expressed after x

Question

Sorry for the bad title, as English is not my main language. Let me explain better what I mean.

I have this equation of parabola: $y = x^2 + 4x $

What I want to do is get the $x$ in one side and express it in relation to $y$ so that the equation takes this form:

$x = g(y)$

How do I proceed doing that?

You could complete the square and then solve for $x$ – Nabigh Sep 16 '14 at 08:41 — Nabigh, Sep 16 '14 at 08:41
add 4 on both sides and try to solve for x – Jasser Sep 16 '14 at 08:43 — Jasser, Sep 16 '14 at 08:43

score 0 · Accepted Answer · answered Sep 16 '14 at 08:42

0

just add 4 on both sides

$y+4=x^2+4x+4$

$\implies (y+4)=(x+2)^2$

$\implies (x+2)=(y+4)^{1/2}$

$\implies x=(y+4)^{1/2}-2$

answered Sep 16 '14 at 08:42

Jasser

Oh, it was that easy after all. Didn't think of completing the square. Thanks a lot! – mihachris Sep 16 '14 at 08:47

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