别用+号,不然就无限循环下去了,没得做的.定义新运算“+”如下：a”+”b=ab-a+b,则(x-1)”+”(2x+3)=(x-1)(2x+3)-(x-1)+(2x+3)=2x^2+x-3-x+1+2x+3=2x^2+2x+1