若x²+3x+4=0,则x²+3x-4= ;若x²+3x+4=0,则2x²+6x-5=
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若x²+3x+4=0,则x²+3x-4=;若x²+3x+4=0,则2x²+6x-5=若x²+3x+4=0,则x²+3x-4=;若x²
若x²+3x+4=0,则x²+3x-4= ;若x²+3x+4=0,则2x²+6x-5=
若x²+3x+4=0,则x²+3x-4= ;若x²+3x+4=0,则2x²+6x-5=
若x²+3x+4=0,则x²+3x-4= ;若x²+3x+4=0,则2x²+6x-5=
若x²+3x+4=0
则x²+3x=- 4
x²+3x-4= -8
则2x²+6x-5
=2(x²+3x)-5
=-8-5
= -13