解：
x²-4x-1=0
(2x-3)²-(x+y)(x-y)-y²
=4x²-12x+9-x²+y²-y²
=3x²-12x+9
=3(x²-4x-1)+12
=3·0+12
=12
x²-4x-1=0
(2x-3)²-(x+y)(x-y)-y²
=4x²-12x+9-x²+y²-y²
=3x²-12x+9
=3(x²-4x-1)+12
=3·0+12
=12
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第1个回答 2015-11-11
(2x - 3)^2 - (x + y)(x - y) - y^2
=4x^2 - 12x + 9 - x^2 + y^2 - y^2
=3x^2 -12x + 9
= 3(x^2 - 4x - 1) + 3 + 9
= 3* 0 + 3 + 9
=12
=4x^2 - 12x + 9 - x^2 + y^2 - y^2
=3x^2 -12x + 9
= 3(x^2 - 4x - 1) + 3 + 9
= 3* 0 + 3 + 9
=12
第2个回答 2015-11-11
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第3个回答 2015-11-11
第4个回答 2015-11-11
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