Finding E((X-2)²) This is a practice quiz as I have a test in a few days. 
I've already completed the first and second questions and my answers are: 
(1) h = 0.4
(2) k = 30
I'm struggling on question 3, I know how to find E(X) using the x•p(x) method but how do I find E((X-2)²). I tried (X-2)²•p(x) but I'm not sure that it's the correct answer. Any help is greatly appreciated!]1

$\begin{align}E[(X-2)^2] &= E[X^2-4X+4]\\
&= E[X^2]-4E[X]+E[4]\\
&= \sum_xx^2p(x)-4\sum_xxp(x)+4\\
&= 93.8 - 4\times4+4\\
&= 81.8 
\end{align}$
On a side note: $E[g(X)]=\displaystyle{\sum_x}g(x)p(x)$.
