Question

y^2 - x^2 - x^3 = 0
When x = 2/3

Answer 1

When x = 2/3, you get
y^2 - 4/9 - 8/27 = 0
y^2 -20/27 = 0
y^2 = 20/27
y = +/- sqrt (20/27)

Answer 2

y =+/- 2*sqrt(15)/9

Answer 3

According to my professor it's supposed to be
(2*sqrt(3))/9 or (2*3^(1/2))/9
and
-(2*sqrt(3))/9 or -(2*3^(1/2))/9

But hoooow? :P

Answer 4

Simplifying what I wrote gives you what your professor said.

Answer 5

They are all equivalent.

Answer 6

Your welcome.

Answer 7

could you show us how that simplification works?

Answer 8

2 * 3^1/2 does not = (2*sqrt(15))/9

Answer 9

Ah damn, I wrote something wrong in the original post! It's supposed to be:
y^2 - x^2 + x^3 = 0
It's a pluss sign before x^3

Answer 10

Anyone? :)

Answer 11

So, you get y^2 - 4/9 + 8/27 = 0
y^2 - 4/27 = 0
y = +/- sqrt (4/27)
or y = +/- 2/(3 sqrt(3))

Answer 12

Note: sqrt (4/27) = sqrt(4)/sqrt(27)

Sqrt (4) = 2
Sqrt (27) = sqrt (9) timkes sqrt(3) = 3 sqrt (3)

Answer 13

Ah! Now I get it! Thanks a lot!^^

Answer 14

You're welcome!