x²-(2n+1)x+n²+n
=x²-(2n+1)x+n(n+1)
=[x-(n+1)](x-n)能写出步骤的名称吗x²-(2n+1)x+n²+n=x²-(2n+1)x+n(n+1) 这个就是化简吧=[x-(n+1)](x-n) 十字相乘分解