maths
2010-03-21 4:55 am
1 Expand (1-2y)^n in ascending powers of y as far as the term in y^3, where n is a positive integer.
回答 (2)
2010-03-21 5:01 am
✔ 最佳答案
1 Expand (1-2y)^n in ascending powers of y as far as the term in y^3, where n is a positive integer.
nC3 = n!/3!(n-3)!
= n(n-1)(n-2)/6
(1-2y)^n
= 1 - 2ny + 4(nC2)y^2 - 8(nC3)y^3+...
= 1 - 2ny + 4n(n-1)y^2/2 - 8n(n-1)(n-2)y^3/6 +...
= 1 - 2ny + 2n(n-1)y^2 - 4n(n-1)(n-2)y^3/3 + ...
參考: Hope can help you^^”
2010-03-21 6:33 pm
火車對撞聽過嗎?
6C3 = (6x5x4)/(1x2x3)
9C4 = (9x8x7x6)/(1x2x3x4)
nC3 = [n(n-1)(n-2)]/(1x2x3)
6C3 = (6x5x4)/(1x2x3)
9C4 = (9x8x7x6)/(1x2x3x4)
nC3 = [n(n-1)(n-2)]/(1x2x3)
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