求教一道数学prep

wenbowei911

If x and y are integers greater than 1, is x a multiple of y?

(1) 3y^2+7y=x
(2) X^2-X is a multiple of y.

The answer is A.

我的理解是multiple是乘数的意思,也就是说x乘以一个数字才等于y,但貌似题目的答案需要的理解和我的相反,应该是y乘以一个数等于x...实在不懂,求教~~~

zhaoyiqing

When x is a multiple of y, x = k * y, k is an integer bigger than 1.

winny0821

multiple 倍数

C  1）的证明是米有神马问题的
2）：X^2-X is a multiple of y. so assume (X^2-X)/y=K (K is an integer). >>>>(x-1)*x/y = k>>>>>>x/y = k/x-1
and k/x-1 is not necessarily an integer. so NOT Sufficient
so the answer is A
note that multiple 的意思是“倍数”

wenbowei911

谢谢大家~