啦啦啦
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0.999999999.....（无限）=1因为0.9=1-.01,0.99=1-0.01,0.999=1-0.001，以此类推，0.9999999 ...(n个9)=1-0.1^n，取极限0.999999999.....（无限）=1两边同时乘以90，所以1*90＝0.999999……*90
——
0.999999999.....（无限）=1因为0.9=1-.01,0.99=1-0.01,0.999=1-0.001，以此类推，0.9999999 ...(n个9)=1-0.1^n，取极限0.999999999.....（无限）=1两边同时乘以90，所以1*90＝0.999999……*90
