若4x^2-4x-15

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若4x^2-4x-15若4x^2-4x-15若4x^2-4x-154x^2-4x-154x^2-4x-15(2x-5)(2x+3)则2x-5或2x+3√(4x^2-12x+9)+√(4x^2-20x+

若4x^2-4x-15
若4x^2-4x-15

若4x^2-4x-15
4x^2-4x-15

4x^2-4x-15<0
(2x-5)(2x+3)<0

2x-5<0

2x+3<0
√(4x^2-12x+9)+√(4x^2-20x+25)
=√((2x - 3)^2)+√((2x-5)^2)
=2x-3-(2x-5)
=2x-3-2x+5
=2