GRE
$$C_{12}$$
($$49^{7}$$)$$C_{26}$$
The sum of the terms in the sequence
51
20!+19!+18!
400(18!)
k
1-x
The number of integer solutions of the equation $$3x^{2}+5x-2=0$$
1
25000 +道题目
199本备考书籍