求下列各二次方程的根(要列齊式)

1.
(x-3)(x-7)=0
x=3 or x=7

2.
x(x+3)=0
x=0 or x=-3

3.
(2x-3)(x+1)=0
2x-3=0 or x+1=0
x=3/2 or x=-1

4.
(3x-5)(3x+4)=0
3x-5=0 or 3x+4=0
x=5/3 or x=-4/3

5.
5(3x+11)(4x+7)(2x-1)=0
(3x+11)(4x+7)(2x-1)=0
3x+11=0 or 4x+7=0 or 2x-1=0
x=-11/3 or x=-7/4 or x=1/2

6.
(2x-5)^2=0
2x-5=0 (repeated roots)
x=5/2 (repeated)

各二次方程的根:


1)(x-3)(x-7)=0
x-3 = 0 or x-7 = 0
x = 3 x = 7
so x = 3 or 7

2)x(x+3)=0
x = 0 or x+3 = 0
x= -.3
so x = 0 or -3

3)(2x-3)(x+1)=0
2x-3=0 or x+1=0
x = 3/2 x = -1
so x = 3/2 or -1

4)(3x-5)(3x+4)=0
3x-50=0 or 3x+4=0
x =50/3 x=4/3
so x =50/3 or 4/3

5 don 't know ` sorry`

6)(2x-5)二次方=0
(2x-5)(2x-5) =0
(2x-5) =0
x = 5/2

2007-08-11 11:32:09 補充：
5)5(3x+11)(4x+7)(2x-1)=0(3x+11)(4x+7)(2x-1)=03x+11=0 or 4x+7=0 or 2x-1=03x=-11 or 4x=-7 or 2x=1x=-11/3 or -7/4 or 1/2//

1)(x-3)(x-7)=0
x-3 = 0 or x-7 = 0
x = 3 x = 7
so x = 3 or 7

2)x(x+3)=0
x = 0 or x+3 = 0
x= -.3
so x = 0 or -3

3)(2x-3)(x+1)=0
2x-3=0 or x+1=0
x = 3/2 x = -1
so x = 3/2 or -1

4)(3x-5)(3x+4)=0
3x-50=0 or 3x+4=0
x =50/3 x=4/3
so x =50/3 or 4/3

5 don 't know ` sorry`

6)(2x-5)二次方=0
(2x-5)(2x-5) =0
(2x-5) =0
x = 5/2

唔多明~係唔係要下列呢個答案??

(x-3)(x-7)=x(x-7)-3(x-7)
=x二次-7x-3x+21
=x二次-10x+21

係唔係咁呀??

1) (x-3)(x-7)= 0
x-3=0
x= 3
OR
x-7=0
x=7
so x= 3 or 7

2) x(x+3)=0
x=0
OR
x+3=0
x= -3
so x= 0 or -3

3) (2x-3)(x+1)=0
2x-3=0
2x=3
x=1.5
OR
x+1=0
x= -1
so x=1.5 or -1

4) (3x-5)(3x+4)=0
3x-5=0
3x=5
x= 1 2/3
OR
3x+4=0
3x=-4
x= -1 1/3
so x= 1 2/3 or -1 1/3

5) 5(3x+11)(4x+7)(2x-1)=0
3x+11=0
3x=-11
x= -3 2/3
OR
4x+7=0
4x=-7
x= -1 3/4
OR
2x-1 = 0
2x=1
x=0.5
so x= -3 2/3 or -1 3/4 or 0.5

6) (2x-5)^2 = 0
2x-5=0
2x=5
x=2.5
so x=2.5

1)(x-3)(x-7)=0
x-3=0 or x-7 =0
x=3 or 7//

2)x(x+3)=0
x=0 or x+3=0
x=-3 or 0

3)(2x-3)(x+1)=0
2x-3=0 or x+1=0
2x=3 or x=-1
x=-1 or 3/2//

4)(3x-5)(3x+4)=0
3x-5=0 or 3x+4=0
3x=5 or 3x =-4
x=-4/3 or 5/3

5)5(3x+11)(4x+7)(2x-1)=0
(3x+11)(4x+7)(2x-1)=0
3x+11=0 or 4x+7=0 or 2x-1=0
3x=-11 or 4x=-7 or 2x=1
x=-11/3 or -7/4 or 1/2//

6)(2x-5)^2=0
(2x-5)(2x-5)=0
2x-5=0 or 2x-5=0
2x=5 or 2x=5
x=5/2//(二重根)