求和:Sn=1+3x+5x*x+7x*x*x+……+(2n-1)x^n-1 (x不为0和1)
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求和:Sn=1+3x+5x*x+7x*x*x+……+(2n-1)x^n-1 (x不为0和1)
Sn=1+3x+5x*x+7x*x*x+……+(2n-1)x^n-1
x*Sn=x+3x^2+5x^3+.+(2n-3)x^(n-1)+(2n-1)x^n
xSn-Sn=(2n-1)x^n-(2x+2x^2+.+2x^(n-1))-1
(x-1)Sn=(2n-1)x^n-2x*(1-x^(n-1))/(1-x)-1
Sn=[(2n-1)x^n-2x*(1-x^(n-1))/(1-x)-1]/(x-1)
=(2n-1)x^n/(x-1)-2x(1-x^(n-1))/(x-1)^2-1/(x-1)
x*Sn=x+3x^2+5x^3+.+(2n-3)x^(n-1)+(2n-1)x^n
xSn-Sn=(2n-1)x^n-(2x+2x^2+.+2x^(n-1))-1
(x-1)Sn=(2n-1)x^n-2x*(1-x^(n-1))/(1-x)-1
Sn=[(2n-1)x^n-2x*(1-x^(n-1))/(1-x)-1]/(x-1)
=(2n-1)x^n/(x-1)-2x(1-x^(n-1))/(x-1)^2-1/(x-1)
求和:Sn=1+3x+5x*x+7x*x*x+……+(2n-1)x^n-1 (x不为0和1)
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求和:Sn=1+3x+5x+7x+...+(2n-1)x^(n-1)谢谢了,
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