问答题
8x1x4+2x3x4+2x2x3-8x2x4.
问答题8x1x4+2x3x4+2x2x3-8x2x4.
x21+3x22-2x1x2+2x1x3-6x2x3.
问答题x21+3x22-2x1x2+2x1x3-6x2x3.
x21+2x1x2+2x22+4x2x3+4x23.
问答题x21+2x1x2+2x22+4x2x3+4x23.