①3(x+1)² —(2x+7)(2x-7)
问题描述:
①3(x+1)² —(2x+7)(2x-7)
答
合并同类项么?
3(x+1)² —(2x+7)(2x-7)
=3(x²+2x+1)-(4x²-49)
=3x²+6x+3-4x²+49
=-x²+6x+52