f3 maths Factorization* 急問*3333* 20分-]共8題,,不懂望解答:)

1. (3m+2n)2 - (2m+n)2
= [(3m+2n)+(2m+n)] [(3m+2n)-(2m+n)]
= (5m+3n) (m+n)

2. 1 + (x-2)3
= [1+(x-2)] [1-(1)(x-2)+(x-2)2]
= (x-1) [-x+3+(x2-4x+4)]
= (x-1) (x2-5x+7)

3. 3m3 - 81n3
= 3 (m3 - 27n3)
= 3 (m-3n) (m+3mn+9n2)

4. (m+1)3 + (m-1)3
= [(m+1)+(m-1)] [(m+1)2 - (m+1)(m-1) + (m-1)2]
= 2m [(m2+2m+1) - (m2-1) + (m2-2m+1)]
= 2m (m2+3)

5. x2 - 25 - 6xy + 9y2
= x2 - 6xy + 9y2 - 25
= (x-3y)2 - 52
= (x-3y+5) (x-3y-5)

6. (x-3y)2 + 2(x-3y) - 15
= [(x-3y)+3] [(x-3y)-5]
= (x-3y+3) (x-3y-5)

7. 2x3 - 16
= 2 (x3 - 8)
= 2 (x-2) (x2+2x+4)

8. 2x3 - 13x2 + 36
= (x-2) (2x2-9x-18)
= (x-2) (x-6) (2x+3)

1. (3m+2n)^2-(2m+n)^2
=2((3m+2n)-(2m+n))
=2(m+n)

2. 1+(x-2)^3
=1+3x-6
=3x-5

3. 3m^3-81n^3
=3(3m-81n)
=9(m-27n)

4. (m+1)^3+(m-1)^3
=3(m+1+m-1)
=3*2m
=6m

5.x^2-25-6xy+9y^2
=2x-25-6xy+18y

6.(x-3y)^2+2(x-3y)-15
=4(x-3y)-15
=4x-12y-15

7. 2x^3-16
=6x-16
=2(3x-8)

8. 2x^3-13x^2+36
=6x-26x+36
=-20x+36
=4(5x+9)

I hope I can help you ^ ^

2007-09-02 13:05:19 補充：
sorry i do it wrong