当m-----时,1/3(mx^2y-2xy+3y^2)-2(5x^2y+3xy-1）是二次多项式.1/3(mx^2y-2xy+3y^2)-2(5x^2y+3xy-1）=(m/3-10)x²y+(-2/3-6)xy+y²+2;是二次多项式.∴m/3-10=0;m/3=10;m=30;很高兴为您解答,skyhunter002为您...