(2X+1)平方-(X+3)平方-(X-1)平方+1
=4x^2+4x+1-(x^2+6x+9)-(x^2-2x+1)+1
=4x^2+4x+1-x^2-6x-9-x^2+2x-1+1
=2x^2-8
一楼的改答案.真怀疑是不是看到我答案才改的.