因式分解..唔識做

1) 2m^2 - n^2 + mn
= (2m^2 - 2n^2) + (n^2 + mn)
= 2(m + n)(m - n) + n(m + n)
= [2(m - n) + n](m + n)
= (2m - n)(m + n)

2) 2a^2 - 18b^2
= 2(a^2 - 9b^2)
= 2[a^2 - (3b)^2]
= 2(a + 3b)(a - 3b)

3) m^2(1 - n)^2 - m^2n^2
= [m(1 - n) + (mn)][m(1 - n) - (mn)]
= m(m - 2mn)
= m^2(1 - 2n)

4) 18x^2 - 24x + 8
= 2(9x^2 - 12x + 4)
= 2[(3x)^2 - 2(3x)(2) + (2)^2]
= 2(3x + 2)^2

5) 50x^2 + 40xy + 8y^2
= 2(25x^2 + 20xy + 4y^2)
= 2[(5x)^2 - 2(5x)(2y) + (2y)^2]
= 2(5x + 2y)^2

6) 8x^2 - 4xy + 1/2y^2
= 2(4x^2 - 2xy + 1/4y^2)
= 2[(2x)^2 - 2(2x)(1/2y) + (1/4y)^2]
= 2(2x + 1/4y)^2

1) 2m^2-n^2+mn
=(2m-n)(m+n)
[2m^2+mn-n^2,,,,,,呢條係2次方程,就甘因式分解就得la]

2) 2a^2 - 18b^2
=2[a^2 - (3b)^2]
=2(a+3b)(a-3b)

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

4)18x^2 - 24x +8
=2(9x^2 - 12x +4)
=2(3x-2)^2

5)50x^2 + 40xy +8y^2
=2(25x^2 + 20xy +4y^2)
=2(5x+2y)^2

6) 8x^2 - 4xy +1/2y^2
=16x^2 - 8xy +y^2
=(4x-y)^2

2007-09-12 14:37:19 補充：
第6條,,,如果你唔想倍大佢,,,或者唔可以倍大佢,,,可以這樣做:8x^2 - 4xy 1/2y^2 =(4x-y)(2x-1/2y)

1) 2m^2 - n^2 + mn
= (2m^2 - 2n^2) + (n^2 + mn)
= 2(m + n)(m - n) + n(m + n)
= [2(m - n) + n](m + n)
= (2m - n)(m + n)

2) 2a^2 - 18b^2
= 2(a^2 - 9b^2)
= 2[a^2 - (3b)^2]
= 2(a + 3b)(a - 3b)

3) m^2(1 - n)^2 - m^2n^2
= [m(1 - n) + (mn)][m(1 - n) - (mn)]
= m(m - 2mn)
= m^2(1 - 2n)

4) 18x^2 - 24x + 8
= 2(9x^2 - 12x + 4)
= 2[(3x)^2 - 2(3x)(2) + (2)^2]
= 2(3x + 2)^2

5) 50x^2 + 40xy + 8y^2
= 2(25x^2 + 20xy + 4y^2)
= 2[(5x)^2 - 2(5x)(2y) + (2y)^2]
= 2(5x + 2y)^2

6) 8x^2 - 4xy + 1/2y^2
= 2(4x^2 - 2xy + 1/4y^2)
= 2[(2x)^2 - 2(2x)(1/2y) + (1/4y)^2]
= 2(2x + 1/4y)^2