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112桃園聯招

回覆 19# jperica05 的帖子

填充2
anbn的公差分別為d , D
Sn=22a1+(n1)dnTn=22b1+(n1)Dn 
SnTn=2a1+(n1)d2b1+(n1)D=4n22n+1
S1T1=a1b1=23故可設a1=3kb1=2k其中k=0
S2T2=6k+d4k+D=655D6d=16k
S3T3=6k+2d4k+2D=71014D20d=32k
32k = 2( 5D - 6d ) = 14D - 20d , 可得 D = 2d
16k = 5D - 6d = 4d , d = 4k
求值式=a1+9db1+2D+b1+17D+a1+10db1+5D+b1+14D=2a1+19d2b1+19D=4k+38d6k+19d=4k+384k6k+194k=82k156k=7841

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