求详解,式子已知A=y²-ay-1,B=2by²-4y-1,且多项式2A-B的值与字母y的取值无关,求2(a²b-1)-3a²b+2的值
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![求详解,式子已知A=y²-ay-1,B=2by²-4y-1,且多项式2A-B的值与字母y的取值无关,求2(a²b-1)-3a²b+2的值](/uploads/image/z/13292441-17-1.jpg?t=%E6%B1%82%E8%AF%A6%E8%A7%A3%2C%E5%BC%8F%E5%AD%90%E5%B7%B2%E7%9F%A5A%3Dy%26%23178%3B-ay-1%2CB%3D2by%26%23178%3B-4y-1%2C%E4%B8%94%E5%A4%9A%E9%A1%B9%E5%BC%8F2A-B%E7%9A%84%E5%80%BC%E4%B8%8E%E5%AD%97%E6%AF%8Dy%E7%9A%84%E5%8F%96%E5%80%BC%E6%97%A0%E5%85%B3%2C%E6%B1%822%EF%BC%88a%26%23178%3Bb-1%EF%BC%89-3a%26%23178%3Bb%2B2%E7%9A%84%E5%80%BC)
求详解,式子已知A=y²-ay-1,B=2by²-4y-1,且多项式2A-B的值与字母y的取值无关,求2(a²b-1)-3a²b+2的值
求详解,式子
已知A=y²-ay-1,B=2by²-4y-1,且多项式2A-B的值与字母y的取值无关,求2(a²b-1)-3a²b+2的值
求详解,式子已知A=y²-ay-1,B=2by²-4y-1,且多项式2A-B的值与字母y的取值无关,求2(a²b-1)-3a²b+2的值
解由2A-B
=2(y^2-ay-1)-(2by^2-4y-1)
=2y^2-2ay-2-2by^2+4y+1
=(2-2b)y^2+(-2a+4)y-1
由多项式2A-B与字母y无关
则2-2b=0且-2a+4=0
即b=1,a=2
故2(a^2b-1)-3a^2b+2
=2a^2b-2-3a^2b+2
=-a^2b
=-(2)^2*1
=-4
∵2(a²b-1)-3a²b+2=-a²b
又2A-B=2(y²-2ay-2)-(by²-4y-1)=(2-2b)y²+(4-2a)y-1
且2A-B的值与Y无关
∴2-2b=0,4-2a=0
∴b=1,a=2
∴-a²b=-2²×1=-4