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**o_O** If a function is even (i.e. symmetric about the y-axis), then: $\displaystyle f(x) = f(-x)$, i.e. if you plug in -x to your function, you'll get the same function if you plugged in x.

If a function is odd (i.e. symmetric about the origin), then: $\displaystyle f(-x) = -f(x)$, i.e. if you plug in -x to your function, then you'll get the negative of f(x).

Show us your work and we'll point out any errors.

As for the circle, given $\displaystyle (x-a)^2 + (y-b)^2 = r^2$, the centre is given by $\displaystyle (a,b)$ (note the minus signs in front of them in the equation). For example, $\displaystyle (x - 5)^2 + (y + 2)^2 = 9$ has centre $\displaystyle (5, {\color{red}-}2)$