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**Natalie11391** Ok so I have a PMF of X:

$\displaystyle P_X(x) = x^2/a$ for $\displaystyle x = -3, -2, -1, 0, 1, 2, 3,$

$\displaystyle 0, otherwise.$

(sorry - I don't really know how to write the PMFs on here but that was my best attempt)

we had to work out a which I have as 28, and then $\displaystyle E[X]$ which I got to be 0.

However now I have to work out the PMF of Y if $\displaystyle Y = (X - E[X])^2$

I really don't know how to approach this! I know it's something really simple but I can't think how I would do this!

I know that as the expectation is 0, $\displaystyle Y = X^2$

but from there I am unsure of how to get the PMF.