问三个今年3月的机井

1。27) 直线XY 的斜率为MN 问X 平行与Y 否A M+N= -1 BM*N=1/4
Answer: c
不需要考虑直线x，y重合的情况吗？当ets给出直线x和y时，它是指两条直线是非重合的直线吗？
2。4. A minimum payment on a credit card acount is x or 5 percent of the y, the balance of the credit card account. What is the minimum payment, X or 5 pct of Y.
1) 10x=y 2) y=200
【确认】B.
由题意X=0.05Y.
note: 如何能从题目得出x＝0。05y呢？不太明白

26) 53 is the standard deviation of T(一数列) greater than S(一数列) ?
(1) mean of T is greater than that of S
(2) median of T is greater than that of S
Answer: A
note：能讲一下基本思路吗？

本来计划五月考，一下就托到了八月了，郁闷ing....