4.Why does the woman plan to go to town?

A.To pay her bills in the bank.

B.To buy books in a bookstore.

C.To get some money from the bank.

3.What does the woman mean?

A.Cathy will be at the party.

B.Cathy is too busy to come.

C.Cathy is going to be invited.

2.Where are the speakers?

A.In a restaurant.

B.In a hotel.

C.In a school.

200．向量的垂直

非零復(fù)數(shù)，對應(yīng)的向量分別是，，則

　 的實部為零為純虛數(shù)

　(λ為非零實數(shù)).

199．復(fù)平面上的兩點間的距離公式

(，).

198．復(fù)數(shù)的乘法的運(yùn)算律

對于任何，有

交換律:.

結(jié)合律:.

分配律: .

197．復(fù)數(shù)的四則運(yùn)算法則

(1);

(2);

(3);

(4).

196．復(fù)數(shù)的模(或絕對值)

==.

195．復(fù)數(shù)的相等

.()