已知A=2x+4xy-2x-3,B=-x²+xy+2,且3A+6B的值与x无关,求y的值.
问题描述：
已知A=2x+4xy-2x-3,B=-x²+xy+2,且3A+6B的值与x无关,求y的值.
答
3A+6B
=6x²+12xy-6x-9-6x²+6xy+12
=18xy-6x+3
=(18y-6)x+3和x无关
所以x系数为0
18y-6=0
y=1/3
答
已知A=2x^2+4xy-2x-3,B=-x²+xy+2,且3A+6B的值与x无关
3A+6B
=3(2x^2+4xy-2x-3)+6(-x²+xy+2)
=6x^2+12xy-6x-9-6x²+6xy+12
=18xy-6x+3
=(18y-6)x+3
(18y-6)=0
y=1/3