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y^2 =1- x blir det det samme som y =(1-x) (1-x) ???

[tex]y^2 =1- x [/tex]
dvs
[tex]y\neq (1-x) (1-x) [/tex]
============
men
[tex]y =\pm\sqrt{1- x}[/tex]

Nice surprise about this shorter form. Can you tell us what it is you are talking/writing about?
Has any info. about this shorter form been posted before (and i just missed it)?

angileena wrote:Nice surprise about this shorter form. Can you tell us what it is you are talking/writing about?
Has any info. about this shorter form been posted before (and i just missed it)?

I'm not entirely sure what you're referring to with "the shorter form", but in this case, we want to solve the equation with respect to y, so given [tex]y^2 = 1-x[/tex], we want to take the square root of both sides, giving us:

[tex]\sqrt{y^2} = \pm\sqrt{1-x}[/tex]

Then, taking the square root of a quadratic term leaves us with a first-degree term.

[tex]y = \pm\sqrt{1-x}[/tex]

The [tex]\pm[/tex] sign is adopted on the right-hand side because [tex](1-x)^2 \ = \ (-(1-x))^2[/tex], because a negative squared term will always yield the same result as the positive squared term. For instance [tex]3^2 \ = \ (-3)^2[/tex]