(1+0.228-0.21)x(0.228-0.221+0.2003)-(1+0.228-0.21+0.2003)x(0.228-0.21)怎么样巧算

设A=0.228-0.21
则：原式=(1+A)(A+0.2003)-(1+A+0.2003)A
=A+A^2+0.2003A+0.2003-A-A^2-0.2003a
=0.2003内个·····^←这是啥意思？？【好吧，我数学很烂·····】我是小学生，老师可能会怀疑吧······