=("-" 1/2+√3/2 i)(7-i)=(√3 "-" 7)/2+(7√3+1)/2i.
(2)("(" √2+√2 i")" ^2 "(" 4+5i")" )/("(" 5"-" 4i")(" 1"-" i")" )=(4i"(" 4+5i")" )/(5"-" 4"-" 9i)=("-" 20+16i)/(1"-" 9i)
=("-" 4"(" 5"-" 4i")(" 1+9i")" )/82
=("-" 4"(" 41+41i")" )/82=-2-2i.
10.设复数z满足4z+2¯z=3√3+i,w=sin θ-icos θ,求复数z及|z-w|的取值范围.
解设z=a+bi(a,b∈R),并将其代入条件中,得
4(a+bi)+2(a-bi)=3√3+i,即6a+2bi=3√3+i.
∴{■(6a=3√3 "," @2b=1"," )┤解得{■(a=√3/2 "," @b=1/2 "." )┤
∴z=√3/2+1/2i.
|z-w|=|(√3/2+1/2 i)"-(" sinθ"-" icosθ")" |
=|(√3/2 "-" sinθ)+(1/2+cosθ)i|
=√((√3/2 "-" sinθ)^2+(1/2+cosθ)^2 )
=√(2"-" √3 sinθ+cosθ)=√(2"-" 2sin(θ"-" π/6) ).
∵-1≤sin(θ"-" π/6)≤1,
∴0≤|z-w|≤2.
故所求的z=√3/2+1/2i,|z-w|的取值范围是[0,2].
B组
1.如果一个复数与它的模的和为5+√3i,那么这个复数是0( )
A.11/5 B.√3i C.11/5+√3i D.11/5+2√3i
解析:设z=x+yi(x,y∈R),则|z|=√(x^2+y^2 ).
∵x+yi+√(x^2+y^2 )=5+√3i,
∴{■(x+√(x^2+y^2 )=5"," @y=√3 "," )┤解得{■(x=11/5 "," @y=√3 "." )┤∴z=11/5+√3i.
答案:C
2.导学号88184057若z2+z+1=0,则z2 014+z2 015+z2 017+z2 018的值为( )
A.2 B.-2
C.-1/2+√3/2i D.-1/2±√3/2i