初三数学1.x2-2x-3=02
1。x2-2x-3=0
===> (x-3)(x+1)=0
===> x1=3，x2=-1
2。x2+4x-1=0
===> (x^2+4x+4)-5=0
===> (x+2)^2=5
===> x+2=±√5
===> x1=-2+√5，x2=-2-√5
3。 (x-3)2+2x(x-3)=0
===> (x-3)(x-3+2x)=0
===> (x-3)(3x-3)=0
===> x1=3，x2=1
4。2x2+1=3x
===> 2x^2-3x+1=0
===> (2x-1)(x-1)=0
===> x1=1/2，x2=1
5。 2x2-5x-7=0
===> (2x-7)(x+...全部
1。x2-2x-3=0
===> (x-3)(x+1)=0
===> x1=3，x2=-1
2。x2+4x-1=0
===> (x^2+4x+4)-5=0
===> (x+2)^2=5
===> x+2=±√5
===> x1=-2+√5，x2=-2-√5
3。
(x-3)2+2x(x-3)=0
===> (x-3)(x-3+2x)=0
===> (x-3)(3x-3)=0
===> x1=3，x2=1
4。2x2+1=3x
===> 2x^2-3x+1=0
===> (2x-1)(x-1)=0
===> x1=1/2，x2=1
5。
2x2-5x-7=0
===> (2x-7)(x+1)=0
===> x1=7/2，x2=-1
6。2x(x-1/2)=3
===> 2x^2-x-3=0
===> (2x-3)(x+1)=0
===> x1=3/2，x2=-1
7。
6x2-x=12
===> 6x^2-x-12=0
===> (2x-3)(3x+4)=0
===> x1=3/2，x2=-4/3
8。(x+1)2-(2x-3)=0
===> x^2+2x+1-2x+3=0
===> x^2+4=0
所以原方程没有实数解。收起
