推 jundarn :感恩^^ 08/19 11:12
※ 引述《jundarn (小眼)》之銘言：
: 8*8*8...*8*7*7*...*7*9的數字和
: 8和7各11111個
我猜題目出錯
題目應該是 88...8*77...7*9
8和7各11111個
令 A = 88...8*77...7*9
then A = 99...9*99...9*(8/9)*(7/9)*9
= (10^11111 - 1)^2 * 56 /9
= (56*10^22222 - 112*10^11111 + 56)/9
= (5600...0 - 11200...0 + 56)/9
= 5599...988800...056/9 (11108個9 11109個0)
= 622...20977...784 (11109個2 11109個7)
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