复数及其代数运算

1、复数的概念

i虚数单位,i^{^{2}} = -1

复数:z=x+iy(z=x+yi),xy为实数

实部:Re\left ( z \right )=0z=iyy\neq 0

共轭复数:\overline{x+iy}=x-iyz=0\Leftrightarrow x=y=0z_{1}=z_{2}\Leftrightarrow x_{1}=x_{2},y_{1}=y_{2}

(任意两个复数不能比较大小)

2、复数的代数运算

z_{1}=x_{1}+iy_{1},z_{2}=x_{2}+iy_{2}

(1)加减法

z_{1}\pm +z_{2}=(x_{1}+iy_{1})\pm (x_{2}+iy_{2})=(x_{1}\pm x_{2})+i(y_{1}\pm y_{2})

(2)乘法

z_{1}z_{2}=(x_{1}+iy_{1})(x_{2}+iy_{2})=x_{1}x_{2}+x_{1}iy_{2}+iy_{1}x_{2}-y_{1}y_{2}

         =(x_{1}x_{2}-y_{1}y_{2})+i(x_{1}y_{2}+x_{2}y_{1})

(3)除法

\frac{^{z_{1}}}{z_{2}}=\frac{x_{1}+iy_{1}}{x_{2}+iy_{2}}=\frac{(x_{1}+iy_{1})(x_{2}-iy_{2})}{(x_{2}+iy_{2})(x_{2}-iy_{2})}=\frac{(x_{1}x_{2}+y_{1}y_{2})+i(x_{2}y_{1}-x_{1}y_{2})}{x_{2}^{2}+y_{2}^{2}}

     =\frac{x_{1}x_{2}+y_{1}y_{2}}{x_{2}^{2}+y_{2}^{2}}+i\frac{x_{2}y_{1}+x_{1}y_{2}}{x_{2}^{2}+y_{2}^{2}}

(4)共轭复数的性质

i)    \overline{z_{1}\pm z_{2}}=\bar{z_{1}}\pm \bar{z_{2}},\overline{z_{1}z_{2}}=\bar{z_{1}}\bar{z_{2}}

ii)   \bar{\bar{z_{1}}}=z_{1}

iii)  z\bar{z}=x^{2}+y^{2}=\left | z \right |^{2}

iv)  z+\bar{z}=2x=2Re\left ( z \right ),z-\bar{z}=i2y=2iIm\left ( z \right )

例题

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