Photography Chinese studies

(1) If X people sign up for both the National Society and the Photography Society, the total number of applicants in this class is (7-x).

∫P(ξ> 0)= P(ξ≥ 1)= 1-P(ξ= 0)= 7 10。

∴P(ξ=0)=3 10,∴C27？ 2xC27？ x=3 10,∴(7？ 2x)(6？ 2x)(7？ x)(6？ X) = 3 10, and the solution is x = 2.

Therefore, five students in Class 4 of Senior Two signed up for the club.

(ⅱ)∵P(ξ= 0)= 3 10，P(ξ= 1)= c 12c 13c 25 = 35，P(ξ=2)=C22C25= 1 10。

The list of ∴ξdistribution is:

∴eξ=0×3 10+ 1×35+2× 1 10=45.