分子分母同乘50-70i
原式=(20+30i)(50-70i)/(50+70i)(50-70i)
=(1000+1500i-1400i+2100)/(2500+4900)
=(3100+100i)/7400
=(31+i)/74
复数的运算比如(20+30I)/50+70I
分子分母同乘50-70i
原式=(20+30i)(50-70i)/(50+70i)(50-70i)
=(1000+1500i-1400i+2100)/(2500+4900)
=(3100+100i)/7400
=(31+i)/74