几道 Math JJ

primefang

1 there are two sets, x and y. x is composed of multiples of 2, and y is composed of multiples of 4, is

it possible for interger m be of x while not of y ? (1) m is even. (2)m/2 is odd

文中如没有possible,I choose B, but it is, shall i choose D

2 下面直线方程，哪一个上面有且只有一点X，Y。 X，Y都是整数。
1) y=2x
2) y=(2/5)x+12
3) y=x+1/2
4) y=sqrt(3) * x
5) forget
我选 y= sqrt(3) * x
why???

3.there are 7 women and 5 men. a commitee of exactly 5 members is to be chosen from them and the

commitee should contain exactly 3 women and 2 men, what is the number of possible choosing ways?

(C7,3* C5, 2)/P 5,5 对吗?

4、 经典机经：线形相关题 （48）

那是时么题???

tongxun

1 there are two sets, x and y. x is composed of multiples of 2, and y is composed of multiples of 4, is it possible for interger m be of x while not of y ? (1) m is even. (2)m/2 is odd

文中如没有possible,I choose B, but it is, shall i choose D
--------------------
选D
======================
2 下面直线方程，哪一个上面有且只有一点X，Y。 X，Y都是整数。
1) y=2x
2) y=(2/5)x+12
3) y=x+1/2
4) y=sqrt(3) * x
5) forget
我选 y= sqrt(3) * x
why???
--------------
正确。因为X必为根号3的倍数，才能令题目成立。
=============
3.there are 7 women and 5 men. a commitee of exactly 5 members is to be chosen from them and the commitee should contain exactly 3 women and 2 men, what is the number of possible choosing ways?

(C7,3* C5, 2)/P 5,5 对吗?
------------
应该除以P2，2吧。

primefang

oh, sqrt= square root, i seeeeeee

==============

3.there are 7 women and 5 men. a commitee of exactly 5 members is to be chosen from them and the commitee should contain exactly 3 women and 2 men, what is the number of possible choosing ways?

(C7,3* C5, 2)/P 5,5 对吗?
------------
应该除以P2，2吧。
－－－－－－－－－
我现在觉的应该不用除

tongxun

恩，好象没有再重复排列的现象了。对吗？

primefang

对因为它问的是  possible choosing ways , 而不是组合的可能性,

对了,如果是后者的话,应该除以几呢???

tongxun

要问组合的可能性，题目应该给出，主席、副主席、普通委员的树木让选。