已知x²-4x-1=0,求代数式(2x-3)²-(x+y)(x-y)-y²的值
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已知x²-4x-1=0,求代数式(2x-3)²-(x+y)(x-y)-y²的值
已知x²-4x-1=0,求代数式(2x-3)²-(x+y)(x-y)-y²的值
已知x²-4x-1=0,求代数式(2x-3)²-(x+y)(x-y)-y²的值
解析
(2x-3)²-(x+y)(x-y)-y²
=4x²-12x+9-(x²-y²)-y²
=4x²-12x+9-x²+y²-y²
=3x²-12x+9
=3(x²-4x)+9
=3+9
=12
3的说法是广告