解一元二次方程,谢x2+12x=0,4x2-1=0,x2=7x,x2-4x-21=0,(x-1)(x+3)=12,3x2+2x-1=0

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解一元二次方程,谢x2+12x=0,4x2-1=0,x2=7x,x2-4x-21=0,(x-1)(x+3)=12,3x2+2x-1=0

解一元二次方程,谢x2+12x=0,4x2-1=0,x2=7x,x2-4x-21=0,(x-1)(x+3)=12,3x2+2x-1=0
解一元二次方程,谢
x2+12x=0,4x2-1=0,x2=7x,x2-4x-21=0,(x-1)(x+3)=12,3x2+2x-1=0

解一元二次方程,谢x2+12x=0,4x2-1=0,x2=7x,x2-4x-21=0,(x-1)(x+3)=12,3x2+2x-1=0
x2+12x=0,
x(x+12)=0
x=0, -12

4x2-1=0,
(2x+1)(2x-1)=0
x=-1/2, 1/2

x2=7x,
x(x-7)=0
x=0, 7

x2-4x-21=0,
(x-7)(x+3)=0
x=7, -3

(x-1)(x+3)=12,
x^2+2x-3=12
x^2+2x-15=0
(x+5)(x-3)=0
x=-5, 3

3x2+2x-1=0
(3x-1)(x+1)=0
x=1/3, -1

(x+12)x=0,所以x=12或x=0
4x2=1,开方,2x=1或-1,x=0.5或-0.5
x2-7x=0,x(x-7)=0,x=0或7
(x-7)(x+3)=0,x=7或-3
x2+2x-15=0,(x+5)(x-3)=0,x=-5或3
(3x-1)(x+1)=0,x=3分之一或-1