因式分解問題 急！！！！?
回答 (2)
2015-10-04 6:47 am
✔ 最佳答案
9ai3x² - x - 10 = (3x + 5) (x - 2)
9aii
9x² - 25 = (3x + 5) (3x - 5)
9b
(6x³ - 2x² - 20x) - (27x² - 75)
= 2x (3x² - x - 10) - 3 (9x² - 25)
= 2x (3x + 5) (x - 2) - 3 (3x + 5) (3x - 5) ...... [ 利用 9a 的答案 ]
= (3x + 5) [ 2x (x - 2) - 3 (3x - 5) ]
= (3x + 5) ( 2x² - 4x - 9x + 15 )
= (3x + 5) ( 2x² - 13x + 15 )
= (3x + 5) (x - 5) (2x - 3)
2015-10-04 10:40 am
9(a)(i)
3x^2 -x-10=(x-2)(3x+5)
9(a)(ii)
9x² - 25 = (3x + 5) (3x - 5)
9b
(6x³ - 2x² - 20x) - (27x² - 75)
= 2x (3x² - x - 10) - 3 (9x² - 25)
= 2x (3x + 5) (x - 2) - 3 (3x + 5) (3x - 5)
= (3x + 5) [ 2x (x - 2) - 3 (3x - 5) ]
= (3x + 5) ( 2x² - 4x - 9x + 15 )
= (3x + 5) ( 2x² - 13x + 15 )
= (3x + 5) (x - 5) (2x - 3)
3x^2 -x-10=(x-2)(3x+5)
9(a)(ii)
9x² - 25 = (3x + 5) (3x - 5)
9b
(6x³ - 2x² - 20x) - (27x² - 75)
= 2x (3x² - x - 10) - 3 (9x² - 25)
= 2x (3x + 5) (x - 2) - 3 (3x + 5) (3x - 5)
= (3x + 5) [ 2x (x - 2) - 3 (3x - 5) ]
= (3x + 5) ( 2x² - 4x - 9x + 15 )
= (3x + 5) ( 2x² - 13x + 15 )
= (3x + 5) (x - 5) (2x - 3)
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