6xy-9x²y；3a(b-c)-2(b-c)；m²(x-2)+m(2-x)；4a²+12ab+9b²；16(2m+n)²-8n(2m+n)+n²；x²+3x；3x³y³-x²y³+2x＾4y；m²-4m+3；x²-3xy+2y²；x＾4+4+4x²；16-4x²；3x＾3-6x²+3xy²；x(x-1)-3x+4.谢了 不过我不用了