Question

A={1,2,3,4,5,6,7}
a) cate submultimi cu cel putin 3 elemente?
b) cate submultimi cu cel putin 5 elemente?

Answer 1

Răspuns:

a) 99

b) 29

Explicație pas cu pas:

a)C7 luate cate 3+C7 luate cate 4 +...+C7 luate cate 7=

C7 luate cate 0 +C7 luate cate 1+...+C7 luate cate 7-(C7 luatecate 0+C7 luate cate 1+C7luate cate 2)=

2^7-(1+7+7*6/2)=128-(1+7+21)=128-8-21=120-21=99

b)C7 luate cate 5+C7 luate cate6+C7 luate cate 7=

=C7 luate cate 2+7+1=21+7+1=28+1=29