Curvature of a curve

How do you find the curvature of a curve of $y=2x-x^2$ at the point where $x=1$ ?

If someone could provide me a little step by step, that would be great!

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One can always start with the definitions. How do you define the curvature of $y$ at a point? –  Pedro Tamaroff Aug 17 '13 at 3:10

$$k(x)=\frac{y''}{(1+y'^2)^{3/2}}$$