Rachel M.

asked • 01/13/23

parametric equations I need help

x=9t^2 and y=27t^3

I know what the graph looks like and the equation I came up with was y=x^(3/2). The assignment tells me that is wrong. I tried including the domain of x>= 0, and that was wrong too. The question only wants the equation. I just wanted to know if my answer was actually wrong or if the assignment was messing up.

1 Expert Answer

By:

Inactive Tutor answered • 01/13/23

Tutor
New to Wyzant

See tutors like this
See tutors like this

Hi Rachel - your equation is correct. I'm not sure why you're being marked wrong... unless it's written as root(x3) or some other equivalent expression?

Upvote • 1 Downvote
More
Report

Rachel M.

Thank you, I just wanted to make sure I wasn't going crazy before I emailed my professor.
Report

01/13/23

Inactive Tutor

Good luck! I checked my work also on Desmos and on the Wolfram Alpha website and got the same answer still... lf there's supposed to be a different answer, please share :)
Report

01/13/23

Roger R.

tutor
x = (3t)^2 and y = (3t)^3. The problem here is that the sign of y = (3t)^3 is negative for -∞ < t < 0, while y = x^(3/2) has only non-negative values. The correct equations are x^3 -y^2 = 0 or y^2= x^3 or x = ∛(y²), but not y = x^(3/2) !
Report

01/13/23

Inactive Tutor

Ah I see - yes, I had assumed domain of t was t >=0, when I was checking my work - without an explicit restriction, I should have checked the negative values as well! Thanks for the note.
Report

01/13/23

Still looking for help? Get the right answer, fast.

Ask a question for free

Get a free answer to a quick problem.
Most questions answered within 4 hours.

OR

Find an Online Tutor Now

Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.