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# C4 - Cartesian/Parametric Q help please Tweet

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1. C4 - Cartesian/Parametric Q help please
How would you convert x=t^3 - 8t and y=t^2 into its cartesian form?

I was thinking of sq rotting the y to make root y = 2 but then it could be + or minus?

Thanks
2. Re: C4 - Cartesian/Parametric Q help please
Try squaring the x.
3. Re: C4 - Cartesian/Parametric Q help please
Surely square rooting y would give sqrt(y)=t? then substitute that back into the x formula and replace all t's with sqrt(y)
4. Re: C4 - Cartesian/Parametric Q help please
(Original post by lamalas600)
Surely square rooting y would give sqrt(y)=t? then substitute that back into the x formula and replace all t's with sqrt(y)
but could it not be +/- sq root y?
5. Re: C4 - Cartesian/Parametric Q help please
You don't have to worry about that, as you will be squaring the Y again later on.
6. Re: C4 - Cartesian/Parametric Q help please
squaring the x and then subbing in y would work
7. Re: C4 - Cartesian/Parametric Q help please
(Original post by Mathlete 4 the win)
squaring the x and then subbing in y would work
So squaring the whole of x=t^3 - 8t to get t^6 - 64t^2 = x^2 and then subbing y where you see t^2... so it would be x^2 = y^3 - 64y ?
8. Re: C4 - Cartesian/Parametric Q help please
(Original post by Cleoleo)
So squaring the whole of x=t^3 - 8t to get t^6 - 64t^2 = x^2
Have another go:

9. Re: C4 - Cartesian/Parametric Q help please
(Original post by Cleoleo)
So squaring the whole of x=t^3 - 8t to get t^6 - 64t^2 = x^2 and then subbing y where you see t^2... so it would be x^2 = y^3 - 64y ?
Yeah as ghostwalker has said you haven't quite expanded it correctly but after that you have the right idea. Just expand it as you would normally making sure not miss any terms.