中三數學...好易..但我都吾識==

1)x^2+ax-y^2+ay
= x^2-y^2 +ax+ay
= (x-y)(x+y)+ a(x+y)
=(x+y)(x-y+a)

2)9-16x^4
=(3-4x)(3+4x)

3)25-10x+x^2
=(x-5)^2

4)9y^2+1+6y
=(3y+1)^2

5) 3x^2-30xy+75y^2
=3(x^2-10xy+25y^2)
=3 (x-5)^2

6) (a-1)^2-4(a-1)+4
=[(a-1)+2]^2
= (a+1)^2

7)16a^4-72a^2b^2+81b^4
=(4a^2 -9b^2)^2

2007-10-14 18:27:59 補充：
快而準,有咩問題即管問丫,努力

1)x^2+ax-y^2+ay
=,(x+y)(x-y)+(a)(x+y)
=(x+y)(x-y+a)

2)9-16x^4
=(3-4x^2)(3+4x^2)

3)25-10x+x^2
=(x-5)(x-5)
=(x-5)^2

4)9y^2+1+6y
=(3y+1)(3y+1)
=(3y+1)^2

5)3x^2-30xy+75y^2
=(x-5y)(3x-15y)

6)(a-1)^2-4(a-1)+4
=[(a-1)-2][(a-1)-2]
=(a-3)^2

7)16a^4-72a^2b^2+81b^4
=(4a^2-9b^2)(4a^2-9b^2)
=(4a^2-9b^2)^2




希望我冇打錯字la~~~

2007-10-14 18:35:36 補充：
5)3x^2-30xy+75y^2=(x-5y)(3x-15y)抽common factor所以answer 應該係=3(x-5y)(x-5y)=3(x-5y)^2SORRY!!!!