expand:
x = 代數
(7x^2-6x-1)(3x-5)-(x+6)(2x-3)
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中一數學~ expand
2009-12-19 9:47 am
回答 (1)
2009-12-19 10:44 am
✔ 最佳答案
(7x^2-6x-1)(3x-5)-(x+6)(2x-3)= (7x^2 - 6x - 1)(3x) - (7x^2 - 6x - 1)(5) - [x(2x - 3) + 6(2x - 3)]
= (21x^3 - 18x^2 - 3x) - (35x^2 - 30x - 5) - [(2x^2 - 3x) + (12x - 18)]
= 21x^3 - 18x^2 - 3x - 35x^2 + 30x + 5 - (2x^2 - 3x) - (12x - 18)
=21x^3 - 18x^2 - 3x - 35x^2 + 30x + 5 - 2x^2 + 3x - 12x + 18
= 21x^3 - (18+35+2)x^2 + (- 3 + 30 + 3 - 12)x + 5 + 18
=21x^3 - 55x^2 + 18x + 23
參考: 052
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