4 for the line with equation y=ax+b,the x-intercept os twice the y-intercept
比较the slope of the line 与1/2的大小，答案是D，但算出来是-1/2呀
还有截距为零的情况,所以D.
5 a certain moneymarket account that had a balance of $48000 during all of last monthearned $360 in interest for the month. at what simple annual interestrate did the account earn interest last month?
答案是9%,题目没看懂
意思是一个货币市场上个月共结余48000，用它赚了360的利息，问以年单利计算每年利率是多少?
360*12/48000=9%
