please explain the answers as well

3. Use above result (question 2) to prove via induction that if X1,X2,,Xn are random variables (not necessarily independent) over a sample space , then E[i=1n]=i=1nE[Xi] 4. Prove that if X1 and X2 are indendpent random variables over a sample space , then Var[X1+X2]=Var[X1]+Var[X2]. (Hint: Use the following fact Var[X]=E[X2](E[X])2)