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1. Let an = 2n-1 for n > 0. Let bn = ∑r+s≤n aras. Find bn - bn-1, bn - 2bn-1 and bn.
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2. Show that 1 - 1/k ≤ n(k1/n - 1) ≤ k - 1 for all positive integers n and positive reals k.
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3. Let a1 = 1, a2 = 2a1, a3 = 3a2, a4 = 4a3, ... , a9 = 9a8. Find the last two digits of a9.
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4. Find all polynomials p(x) such that p(x2) = p(x)2 for all x. Hence find all polynomials q(x) such that q(x2 - 2x) = q(x-2)2.
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5. Find the smallest positive real t such that x1 + x3 = 2t x2, x2 + x4 = 2t x3, x3 + x5 = 2t x4 has a solution x1, x2, x3, x4, x5 in non-negative reals, not all zero.
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6. For which n can we find positive integers a1, a2, ... , an such that a12 + a22 + ... + an2 is a square?
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