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Using binomial theorem prove that 6^n-5n...

Using binomial theorem prove that `6^n-5n` always leaves remainder I when divided by 25.

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`6^(n)-5n =(1+5)^(n) -5n`
`= (1+5n+.^(n)C_(2).5^(2)+.^(n)C_(3)5^(3)+"…..")-5n`
`= 25(.^(n)C_(2)+.^(n)C_(3)+"……")+1`
Hence, `6^(n) - 5n` when divided by 25 leaves 1 as remainder.
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