`1)M=(1+1/2)(1+1/3)(1+1/4)...(1+1/10)(1+1/11)`
`M=3/2*4/3*5/4*....*11/10*12/11`
`M=(3.4.5....12)/(2.3.4....11)`
`M=12/2=6`
`=>1/M=1/6`
`2)M=125^7-625^5-25^9`
`M=(5^3)^7-(5^4)^5-(5^2)^9`
`M=5^21-5^20-5^18`
`M=5^18(5^3-5^2-1)`
`M=5^18(125-25-1)`
`M=99.5^18\vdots 99=>dpcm`
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