A solution to the congruency 4x 9 mod 13 is A x 12modl3 B

A solution to the congruency 4x = 9 mod 13 is: A. x = 12modl3 B. x = 9mod13 C. x = 8modl3 D. x = 10modl3 7. The expression (n = 1)/k[n k - 1], where n N - {0}, equals: A. (n + 1 k + 1) B. (n k - 1) C. (n + 1 k) D. (n k)

Solution

7. (n+1)/k[nCk-1]

= [(n+1)/k][n!/(k-1)!(n- (k-1))!

= [(n+1)/k][n!/(k-1)!(n+1 -k)!

= (n+1)!/(k!)(n+1 -k)^!

= n+1Ck

Option C

8. P(4,2)*C( 3,2)

= (4!/2!)(3!/2!1!)

= (4*3*3)

= 36

Option D