How does one prove the formula: var(X) = E(X2) − E2(X)? Thanks!
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$\displaystyle \displaystyle V(X) = E(X-\mu)^2 = E(X^2 - 2 \mu X + \mu^2) $ $\displaystyle = E(X^2) - 2 \mu E(X) + E(\mu^{2}) $ $\displaystyle = E(X^2) - 2 \mu^{2} + \mu^{2} = E(X^2) - \mu^{2} $
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