AP{an}中d≠0,a1,a3,a9成等比,求a1+a3+a9/a2+a4+a10

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AP{an}中d≠0,a1,a3,a9成等比,求a1+a3+a9/a2+a4+a10

AP{an}中d≠0,a1,a3,a9成等比,求a1+a3+a9/a2+a4+a10
AP{an}中d≠0,a1,a3,a9成等比,求a1+a3+a9/a2+a4+a10

AP{an}中d≠0,a1,a3,a9成等比,求a1+a3+a9/a2+a4+a10
a3=a1+2d
a9=a1+8d
a3/a1=a9/a3
(a1+2d)/a1=(a1+8d)(a1+2d)
4d^2-4a1d=0
d(d-a1)=0
因为d≠0
所以d-4a1=0
d=a1
a3=3a1,a2=2a1,a4=4a1,a9=9a1,a10=10a1
a1+a3+a9/a2+a4+a10=(1+3+9)a1/(2+4+10)a1=13/16

13/16 设A1=1 A3=3 A9=9依次类推

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