Probability - Variance of Random Variable

Ask

If 'E' denotes Expectation, the variance of a random variable X is given by:

(a) E[x^2] - E^2[x]

(b) E[x^2] + E^2[x]

(c) E[x^2]

(d) E^2[x]

Answer is ( a )

Concept

Type Reasoning here