suy ra (1-i)z= (4-5i)-(2-i)

(1-i)z =2-4i

z= (2-4i)/(1-i)

z= 3-i

a) thực =1; ảo =4

b)thực= -7; ảo= 6\(\sqrt{2}\)

c)thực=13; ảo=0

d)thực=1; ảo=7

Choose A, B, C or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions

Mathematics is such important field and serves so many of the sciences that it is a prerequisite for studying every scientific discipline.

A. is

B. such important 

C. it 

D. for studying

I had a red pen but I seem to have lost it; I think I’d better buy ______ one.

A. the other 

B. another 

C. others 

D. the 

3x²-27