Question

已知代数式A=2x²+3xy+2y-1,B=x²-xy+x-1/2 若A-2B的值与x的取值无关，求y的值

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Answer 1

数学导报对吧~
A-2B
=2x²+3xy+2y-1-2(x²-xy+x-1/2)
=2x²+3xy+2y-1-2x²+2xy-2x+1
=5xy-2x+2y
=x(5y-2)+2y
根据题意，结果与x的取值无关
则含x的项为0,
所以，5y-2=0
5y=2
y=五分之二
祝你好运~

Answer 2

A-2B
=2x²+3xy+2y-1-2(x²-xy+x-1/2)
=2x²+3xy+2y-1-2x²+2xy-2x+1
=5xy-2x+2y
=x(5y-2)+2y
根据题意，结果与x的取值无关
则含x的项为0,
所以，5y-2=0
5y=2
y=2/5

Answer 3

A-2B
=2x²+3xy+2y-1-2(x²-xy+x-1/2)
=2x²+3xy+2y-1-2x²+2xy-2x+1
=5xy-2x+2y
=x(5y-2)+2y
y=2/5