f.3 maths!`

1) 4a^2 - 9a^3 +5a
=-a(9a^2-4a+5)
=-a(9a-5)(a+1)


2) 16(a+b)^2-25(a-2b)^2
=[4(a+b)-5(a-2b)][4(a+b)+5(a-2b)]
=(-a+14b)(9a-6b)
=-3(a-14b)(3a-2b)


3a) (m+2)(m-8)+24
=m^2-6m+8
=(m-2)(m-4)

3b) (x^2+x+2)(x^2+x-8)+24
=[(x^2+x)+2][(x^2+x)-8]+24
=(x^2+x-2)(x^2+x-4) [Using (a),m=x^2+x]

2011-01-01 11:45:01 補充：
Correction:
1) 4a^2 - 9a^3 +5a
=-a(9a^2-4a+5)
=-a(9a+5)(a-1)
Alex Chan: Thx for ur reminder~

4a^2 - 9a^3 +5a
=a(4a^2 - 9a^2 + 5 )
= a(-9a^2 + 4a + 5)
= -a(9a+5)(a-5)


16(a+b)^2 - 25(a-2b)^2
= [4(a+b)]^2-[5(a-2b)]^2
=[4(a+b)+5(a-2b)][4(a+b)-5(a-2b)]
=(4a+4b+5a-10b)(4a+4b-5a+10b)
=(9a+6b)(-a+14b)
=-3(3a-2b)(a-14b)

(m+2)(m-8)+24
=m^2-8m+2m-16+24
=m^2-6m+8
=(m-4)(m-2)

Let m=x^2+x
(x^2+x+2)(x^2 +x -8) +24
=(m+2)(m-8)+24
=(m-4)(m-2)
=(x^2+x-4)(x^2+x-2)
=(x^2+x-4)(x-1)(x+2)

1) Factorize 4a^2 - 9a^3 +5a
4a^2 - 9a^3 + 5a
=-a(9a^2-4a-5)
=-a(9a+5)(a-1)

001計錯左