用配方法解下列方程;3x2-2x-3=0 (2x-1)2=x(3x+2)-7

问题描述:

用配方法解下列方程;3x2-2x-3=0 (2x-1)2=x(3x+2)-7

答:
3x2-2x-3=0
3x^2-2x-3=0
3(x^2-2x/3+1/9)-1/3-3=0
3(x-1/3)^2=10/3
(x-1/3)^2=10/9
x-1/3=±√10 /3
x=(1±√10)/3
(2x-1)2=x(3x+2)-7
4x^2-4x+1=3x^2+2x-7
x^2-6x+8=0
x^2-6x+9-9+8=0
(x-3)^2=9-8
(x-3)^2=1
x-3=±1
x=3±1
x=4或者x=2