已知A=2x2 3xy-2x-1,B=-x2 xy-1,且3A 6B的值与x无关,求y的值

\u5df2\u77e5A=2x2+3xy-2x-1,B=-x2+xy-1,\u4e143A+6B\u7684\u503c\u4e0ex\u65e0\u5173\uff0c\u6c42y\u7684\u503c\u3002

\u89e3\uff1a3A = 6x2+9xy-6x-36B = -6x2+6xy-6\u6240\u4ee5 3A+6B = 6x2-6x2+9xy+6xy-6x-3-6 = 15xy-6x-9 = 3x*(5y-2)-9\u5982\u679c\u9700\u8981 3A+6B\u4e0ex\u65e0\u5173\uff0c\u90a3\u4e485y-2\u5c31\u5fc5\u987b\u4e3a0\uff0c\u6545 y = 2/5

3A+6B
=3\uff082X^2+3XY-2X-1\uff09+6\uff08-X^2+XY-1\uff09
=6x^2+9xy-6x-3-6x^2+6xy-6
=15xy-6x-9
=x(15y-6)-9
\u4e0ex\u65e0\u5173
\u5219x\u524d\u7cfb\u6570 =0
15y-6=0
y=2/5

3A+6B
=3(2x²+3xy-2x-1)+6(-x²+xy-1)
=6x²+9xy-6x-3-6x²-6xy-6
=3xy-6x-9
=(3y-6)x-9

3y-6=0
y=2

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