Anil,
For problem 4, use the numbers for x just as they appear — they are allowed to be positive, negative, or zero, and you should follow the same formulas in any case (for example, if x is negative, then the corresponding value in the column xP(x) will also be negative — BUT, because a negative times a negative is positive, the value of x^2 P(X) will be positive)
For problem 5, this is similar to the last example we considered in class on Tuesday last week — start by drawing a tree diagram for the problem. If you’re still stuck, let me know!
Mr. Reitz