Hey guys, homework problem on expectation. This is what i have so far.

Suppose a fair die is rolled ten times. Find numerical values for the expectations of:

1) the number of faces which fail to appear in the ten rolls

Here's what i got:

So the probability that x faces dont is ... this is the part im not sure about.

I know, for example, that would have to be (1/6)^10

After this i am unsure how to proceed. seems like it would NOT be ... I cant figure out how to find a general formula for this.

Thanks in advance!