f(z)
=x³+6x²y-3xy²-2y³+3x²yi+6xy²i-y³i-2x³i+Ci
=x³+3x²yi-3xy²-y³i-2x³i+6x²y+6xy²i-2y³+Ci
=(x+yi)³-2i(x³+3x²yi-3xy²-y³i)+Ci (用到了-1=i²)
=z³-2iz³+Ci
=(1-2i)z³+Ci
f(z)
=x³+6x²y-3xy²-2y³+3x²yi+6xy²i-y³i-2x³i+Ci
=x³+3x²yi-3xy²-y³i-2x³i+6x²y+6xy²i-2y³+Ci
=(x+yi)³-2i(x³+3x²yi-3xy²-y³i)+Ci (用到了-1=i²)
=z³-2iz³+Ci
=(1-2i)z³+Ci