How many proper subsets of set a = {1,2,3,4,5,6,7,8}

Let the number of complete set I be n, the number of its subsets be to the nth power of 2, and the number of proper subsets be to the nth power of 2-1
That is: 2 ^ 8-1 = 255
Add an empty set, 255 + 1 = 256
I'm sorry. I just miscalculated

Why is the number of subsets of n-ary set twice of N?

It's equivalent to taking 0 and 1 from n elements. There are two choices for each element, taking and not taking, so 2 * 2 * 2... A total of N 2 multiplications (empty set is all not taken, complete set is all taken)

62. If the set a = {1,2,3}, B = {1,3,4}, then the number of subsets of a ∩ B is () a, 2,x05b, 3
62. If a = {1,2,3}, B = {1,3,4}, then the number of subsets of a ∩ B is ()
A、2\x05B、3\x05C、4\x05D、16

∵A={1,2,3},B={1,3,4},
∴A∩B={1,3},
Then the number of subsets of a ∩ B is 22 = 4
So choose C

The number of subsets of set a = {1,2,3} is

Because there are three elements in set a
So the number of subsets = 2 & # 179; = 8

How many proper subsets of set a = {1,2,3,4,5,6,7,8}