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The greatest interger by which `1+Sigma_(r=1)^(30) rxxr !` is divisible isA. composite numberB. odd numberC. divisible by 3D. none of these |
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Answer» Correct Answer - D `rxxr!=(r+1-1)xxr!` `=(r+1)!-r!` `=V(r )-V(r-1)` `rArrsum_(r=1)^(30)r(r!)=V(31)-V(0)=(31)!-1` `rArr1+sum_(r=1)^(30)r(r!)=31!` which is divisble by 31, which are prime numbers. |
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