解3x(x²+2x²+1)-x(x-2)(2x+4)=3x(3x²+1)-2x(x-2)(x+2)=9x³+3x-2x(x²-4)=9x³+3x-2x³+8x=7x³+11x(1/3a³+2a²-2/5a)÷(2/3)=(1/3a³+2a²-2/5a)×(3/2)=1/2a...