z = ( 2 - i ) / ( 2 +i ) · ( 2 - i ) + ( 1 - i ) / ( 1 +i ) ·( 1 - i)
cu i² = - 1
( 2 +i ) · ( 2 - i ) = 2² - i² = 4 + 1 = 5
( 1 +i ) ·( 1 - i) = 1 - i² = 1 +1 = 2
z = ( 2 -i ) / 5 + ( 1 - i ) /2 = ( 4 - 2i + 5 - 5i ) / 10 = ( 9 - 7i ) / 10
z = 9 / 10 - 7· i /10
Re(z) = 9 / 10 Im(z) = - 7 / 10