1/3*1+1/3*5+1/5*7+A+1/17*19+1/19*21
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1/3*1+1/3*5+1/5*7+A+1/17*19+1/19*21
1/3*1+1/3*5+1/5*7+A+1/17*19+1/19*21
=1/2[1-1/3]+1/2[1/3-1/5]+...+1/2[1/19-1/21]
=1/2[1-1/3+1/3-1/5+...+1/19-1/21]
=1/2[1-1/21]
=10/21
=1/2[1-1/3]+1/2[1/3-1/5]+...+1/2[1/19-1/21]
=1/2[1-1/3+1/3-1/5+...+1/19-1/21]
=1/2[1-1/21]
=10/21
求(1~+a)(3~+a)(5~+a)...(17~+a)(19~+a)除以(2~+a)(4~+a)(6~+a)...(
(a+1)(a+3)(a+5)(a+7)+15
1+2a+3a^2+4a^3+5a^4+6a^5+5a^6+4a^7+3a^82a^9+a^10
已知a^2+a+1=0,求1+a+a^2+a^3+a^4+a^5+a^6+a^7+a^8的值
已知1+a+a^2=0求1+a+a^2+a^3+a^4+a^5+a^6+a^7+a^8的值
求和:1,a+a^2,a^3+a^4+a^5,a^6+a^7+a^8+a^9,···(a不等于0)
(a+8)(a-8)-(a+3)(a+5)=1
a+a^2+a^3+a^4+a^5+a^6...+a^n=a^n+1-a/a-1 (a-1)≠0
求(2a平方+3a+2)/(a+1)-(a平方-4a-5)/(a+2)-(3a平方-4a-5)/(a-2)+(2a平方a
(2a^2+3a+2)/(a+1)-(a^2-a-5)/(a+2)-(3a^2-4a-5)/(a-2)+(2a^2-8a
当a=1时,a-2a+3a-4a+5a…+99a-100a=
(a 1)(a 2)(a 3)(a