求助prep的ps中两道题。

金大小姐

1. for how many intergers n is 2^n=n^2?

a.none

b.one

c.two

d.three

e.more than three

答案是：C

但自己只想出来了n=2是符合条件的，还有一个是什么呢？？

2. a used-car dealer sold one car at profit of 25 percent of the dealer's purchase price for that car and sold another car at a loss of 20 percent of the dealer's purchase price for that car. If the dealer sold each car for $20,000，what was the dealer's total profit or loss, in dollars, for the two transcations combined?

a.$1,000 profit

b.$2,000 profit

c.$1,000 loss

d.$2,000 loss

e.$3,334 loss

正确答案是：C

但是自己计算的时候是A      (0.25-0.02) *20,000=1,000 明显的profit ，为什么答案是loss呢？？

盼帮助

millions of thanks

wawadream

1. 2^2=2^2 and 4^2=2^4

2.不能那样简单相减。if the purchase price of the two cars is x, y, then

(20000-x）/x=25%=> x=16000

(y-20000)/y=20%，=>y=25000

the purchase price of the two cars is 41000,but the selling price is 40000,so it is a loss of 1000.