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**zorro** Question : If $\displaystyle X_1$ has mean 4 and variance 9 while $\displaystyle X_2$ has mean -2 and variance 5, and the two are independent, determine

i) $\displaystyle E(2X_1 + X_2 -5)$

ii) $\displaystyle Var(2X_1 + X_2 -5)$

My answers are

i) $\displaystyle E(2X_1 + X_2 -5)$ = $\displaystyle 2[E(X_1)] + [E(X_2) -5]$ =$\displaystyle 8 + [-2 -5]$ =$\displaystyle 1$

ii) $\displaystyle Var(2X_1 + X_2 -5)$ = $\displaystyle 2[Var(X_1)] + [Var(X_2) -5]$ = $\displaystyle 2(9) + [5 -5]$ = $\displaystyle 18 + 0$ = $\displaystyle 18$

Is my answer correct and is my method for solving the answer crorect or no