已知:A=2x2+3xy-2x-1,B=-x2+xy-1,且3A+6B的值与x无关,则y的值为_.
问题描述:
已知:A=2x2+3xy-2x-1,B=-x2+xy-1,且3A+6B的值与x无关,则y的值为______.
答
∵A=2x2+3xy-2x-1,B=-x2+xy-1,∴3A=3(2x2+3xy-2x-1)=6x2+9xy-6x-3,∴6B=6(-x2+xy-1)=-6x2+6xy-6,∴3A+6B=(6x2+9xy-6x-3)+(-6x2+6xy-6),=6x2+9xy-6x-3-6x2+6xy-6,=15xy-6x-9,=3x(5y-2)-9.∵3A+6B的...