How do you plot $x = y^2 - 6$ on a graphing calculator?

Question

I have a graphing calculator app (Graphing Calculator+) that only allows me to enter $x$ as a variable, but I need to graph $x = y^2 - 6$.

I haven't used a graphing calculator in awhile. Is this normal? If it is, is there some kind of a trick to graphing this equation?

Your help would be appreciated.

Maybe in parametric form? $x = t^2 - 6, y = t$ for $ -10< t< 10$ — The Chaz 2.0, Apr 20 '12 at 20:57
I use the app Desmos, It's free so I would recommend it @Subtle Array — Ahmed S. Attaalla, Jan 03 '16 at 05:53

score 12 · Accepted Answer · answered Apr 20 '12 at 21:10

12

To plot $x=f(y)$ without having to mentally flip across the $y=x$ diagonal, you could plot $y = -f(x)$, then turn the calculator 90° counterclockwise. In your case, plot $y=-(x^2-6)$.

answered Apr 20 '12 at 21:10

Théophile

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+1 But my calculator is on my iPad and when I turn it 90°, the calculator turns too! :-) – Dilip Sarwate Apr 20 '12 at 21:33
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@DilipSarwate Then turn yourself or wait 18 hours ;-) – dtldarek Apr 20 '12 at 21:35
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How to lock ipad screen :P :) http://www.howtogeek.com/howto/36330/how-to-lock-the-screen-orientation-on-your-ipad-with-ios-4.2/ – Gordon Gustafson Apr 21 '12 at 01:58
@DilipSarwate Five years later, I've solved your problem: just multiply your iPad by $-i$, and then you'll have just a regular Pad that shouldn't change the display when you turn it. ;) – Théophile Apr 10 '17 at 00:35
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The question was answered 9 years ago, but possibly still saved me several points on a test I have in a few days! – Cotton Headed Ninnymuggins Jan 28 '21 at 04:11

Raymond Manzoni · Answer 2 · 2012-04-20T21:07:37.397

7

You may :

graph $y=x^2-6$ and mentally reverse the $x$ and $y$ axis
graph $y=\sqrt{x+6}$ and $y=-\sqrt{x+6}$ obtaining the two required branches
use the parametric method $x=t^2-6,y=t$ proposed by The Chaz! (probably the best solution if it works...)

edited Apr 20 '12 at 21:07

answered Apr 20 '12 at 20:56

Raymond Manzoni

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@Ekuurh: (-: !! sknahT – Raymond Manzoni Apr 20 '12 at 21:02
I can't understand why a modern graphing calculator wouldn't allow me to just enter the equation as is, but this solution works, and it's good mental exercise. Thank you for your reply. – subtlearray Apr 20 '12 at 21:05
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If your brain doesn't have the reversion feature, you can turn it and then hold it up to a mirror :) – Thomas Andrews Apr 20 '12 at 21:06
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@ThomasAndrews: a mirror inclined at 45 degrees! :-) – Raymond Manzoni Apr 20 '12 at 21:08
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Lol. Yeah. It's a minor nitpick, but still. :P – subtlearray Apr 20 '12 at 21:09
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@RaymondManzoni (-: shvpvmou uowwo) h++3^d 3^v s^o^^!W – dtldarek Apr 20 '12 at 21:16
@dtldarek: Thanks for the effort! (Finally I was right not trying to 'Mirror' it! :-)) – Raymond Manzoni Apr 20 '12 at 21:31

score 0 · Answer 3 · answered Jan 02 '16 at 20:55

0

GeoGebra allows entry directly in that form, eg

http://web.geogebra.org/?command=x=y^2-6

answered Jan 02 '16 at 20:55

murkle

411

How do you plot $x = y^2 - 6$ on a graphing calculator?

3 Answers3