已知x^2+4x-1=0,求代数式(2x+1)^2-(x+2)(x-2)-x(x-4)的值

2025-03-22 09:37:00
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回答1:

∵x^2+4x-1=0
(2x+1)^2-(x+2)(x-2)-x(x-4)=4x^2+4x+1-x^2+4-x^2+4x=2x^2+8x+5=2(x^2+4x-1)+7=7