1).Is the integer r divisible by 3? A
(1).r is the product of 4 consecutive positive integers.
(2).r<25
第一个条件怎么算啊？
2). If x and y are integers greater than 1, is x a multiple of y? A
(1).3y2+7y=x
(2).x2-x is a multiple of y
3). If M is a finite set of negative integers, is the total number of integers in M an odd number? B
(1).the product of all the integers in M is odd
(2).the product of all the integers in M is negative
4).Each person attending a fund-raising party for a certain club was charged the same admission fee. How many people attended the party? C
(1). if the admission fee had been $0.75 less and 100 more people had attended, the club would have received the same amount in admission fees.
(2).if the admission fee had been $1.50 more and 100 fewer people had attended, the club would have received the same amount in admission fees.
怎么没人帮忙啊？拜托啊
1).Is the integer r divisible by 3? A
(1).r is the product of 4 consecutive positive integers.
(2).r<25
假设n能被3整除，n+3, n+6....都能被3整除，这个数列的公差是3，所以连续4个整数肯定又能被3整除的数，选A
2). If x and y are integers greater than 1, is x a multiple of y? A
(1).3y2+7y=x
(2).x2-x is a multiple of y
(1)能推出 y(3y+7)=x 因为y是整数，所以x是y的倍数
(2)能推出y是x的倍数
所以选A
3). If M is a finite set of negative integers, is the total number of integers in M an odd number? B
(1).the product of all the integers in M is odd
(2).the product of all the integers in M is negative
很明显 B 奇数个偶数的乘积是负的
4).Each person attending a fund-raising party for a certain club was charged the same admission fee. How many people attended the party? C
(1). if the admission fee had been $0.75 less and 100 more people had attended, the club would have received the same amount in admission fees.
(2).if the admission fee had been $1.50 more and 100 fewer people had attended, the club would have received the same amount in admission fees.
由（1） (x-0.75)*(y+100)=xy
由（2） (x+1.5)*(y-100)=xy
联合两个条件可解，选C (注：x为admission fee y为人数)
建议去看一些基础的概念
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