F.3 Maths 問題

運用了最清楚的步驟....希望你明瞭~

Q1.
4x+ (-7x-8)(x-3)
= 4x + [(-7x)(x) + (-7x)(-3) + (-8)(x) + (-8)(-3)]
= 4x + (-7x^2 + 21x - 8x + 24)
= 4x - 7x^2 + 13x + 24
= -7x^2 + 17x + 24
= -7x^2 -7x + 24x + 24
= -7x (x+1) + 24(x+1)
= (x+1) (-7x+24)

Q2.
2(7-2x)^2 - 14x
= 2(7-2x)(7-2x) - 14x
= 2 [(7)(7) + (7)(-2x) + (-2x)(7) + (-2x)(-2x)] - 14x
= 2 (49 - 14x - 14x + 4x^2) - 14x
= 98 - 56x + 8x^2 - 14x
= 8x^2 - 70x + 98
= 8x^2 - 56x - 14x + 98
= 8x(x-7) - 14(x-7)
= (x-7) (8x-14)

2010-10-01 11:23:59 補充：
Q2.
答案應該再抽埋個2出黎
變成 2(x-7)(4x-7)
但千萬唔好整走佢
因為而家唔係做緊 (x-7)(8x-14) =0
約走個2係會出錯的

(1) (24-7x)(1+x)
(2) 2(x-7)(4x-7)

Q1, 4x+ (-7x-8)(x-3)
=4x+[x(-7x-8)-3(-7x-8)]
=4x-7x^2-8x+21x+24
=-7x^2+17x+24

Q2, 2(7-2x)^2 - 14x
=2[(7)^2-2(7)(2x)+(2x)^2]-14x
=2(49-28x+4x^2)-14x
=98-56x+8x^2-14x
=8x^2-70x+98

2010-09-26 16:51:40 補充：
=-7x^2+17x+24
=(24-7x)(1+x)



=8x^2-70x+98
=(x-7)(4x-7)