1. ## sketching level curves

Hi, I've got a level curve

T(x,y) = 2x - y / x^2 + y^2

at T = 0

If i put T in i get

0 = 2x - y / x^2 + y^2

So what i did at first was multiply out the bottom to get

0 = 2x - y
y=2x

But then i thought of inversing it first before i multiplied out so i got

0 = x^2 + y^2 / 2x - y
x^2 + y^2 = 0

which one is right? am i allowed to inverse it first?

whats goin owwwnnnn?!

2. Originally Posted by jarudo
Hi, I've got a level curve

T(x,y) = 2x - y / x^2 + y^2

at T = 0

If i put T in i get

0 = 2x - y / x^2 + y^2

So what i did at first was multiply out the bottom to get

0 = 2x - y
y=2x Mr F says: Good.

But then i thought of inversing it first before i multiplied out so i got Mr F thinks: Uh oh. Nothing good ever comes from a "But then I thought ...."

0 = x^2 + y^2 / 2x - y Mr F says: Yep, I was right.

This is utter rubbish. How can you possibly take the reciprocal of the left hand side of 0 = 2x - y / x^2 + y^2 and get zero!!! You should know better - isn't this a 2nd year university level mathematics subject you're enrolled in.

x^2 + y^2 = 0

which one is right? am i allowed to inverse it first?

whats goin owwwnnnn?!
This particular assignment question is sure turning up some interesting thinking.

3. haha thanks mr f