F4 Maths Factor Theorem

1. x3-2x2+x-2=0
x2(x-2)+(x-2)=0
x-2=0 or x2+1=0
x=2 or x2=-1(rej.)

2. 2x3-5x2+5x-2=0
2x3-2-5x2+5x=0
2(x2-1)-5x(x+1)=0
2(x-1)(x+1)-5x(x+1)=0
x+1=0 or 2(x-1)-5x=0
x=1- or -3x=2
x=1 or x=-2/3

3. x3+1=0
x3=-1
x=-1

4. x3-1=0
x3=1
x=1

5. x3-8=0
x3=8
x=2

6. x4-1=0
x4=1
x=1 or x=-1

2009-10-25 22:05:42 補充：
where??????!

2009-10-25 22:10:55 補充：
2. 2x^3-5x^2+5x-2=0
2x^3-2-5x^2+5x=0
2(x^2-1)-5x(x-1)=0
2(x-1)(x+1)-5x(x-1)=0
x-1=0 or 2(x+1)-5x=0
x=1 or -3x=-2
x=1 or x=2/3