GRE
$$C_{12}$$
($$49^{7}$$)$$C_{26}$$
The sum of the terms in the sequence
51
$$a_3$$+$$a_4$$+$$a_5$$+$$a_6$$+$$a_7$$
$$\frac{1}{8}$$
The number of different four-digit integers that can be formed by elements from Set A (all the elements can be used by more than once)
The number of different three-digit integers that can be formed by elements from Set B (all the elements can be used by more than once)
x-y
z
25000 +道题目
6本备考书籍