a) . Prove that for every positive integer n, b) 1.2+2.3+...+ n(n+1) = n(n+1)(n+2)/3. Prove that...

   

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a) . Prove that for every positive integer n, b) 1.2+2.3+...+ n(n+1) = n(n+1)(n+2)/3. Prove that 21 divides 4+1 +52n-1 whenever n is a pos- itive integer. a) . Prove that for every positive integer n, b) 1.2+2.3+...+ n(n+1) = n(n+1)(n+2)/3. Prove that 21 divides 4+1 +52n-1 whenever n is a pos- itive integer.