# DKhanh

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# 9 Questions

 25 Prove that every year has at least one Friday the 13th 10 Prove that all even integers $n \neq 2^k$ are expressible as a sum of consecutive positive integers 10 After swapping the positions of the hour and the minute hand, when will a clock still give a valid time? 2 Find the last member remained in game 2 fill the board with dominos

# 429 Reputation

 +5 Find the last member remained in game +10 Prove that all even integers $n \neq 2^k$ are expressible as a sum of consecutive positive integers +25 Prove that every year has at least one Friday the 13th +5 How to find the minimum value of $\frac{x}{2x+3y}+\frac{y}{y+z}+\frac{z}{z+x}$?

 1 How to “efficiently” compute the number of solution of $25x= 5y+8z$ such that $x,y,z \in [0,9]$ and $x,y,z \in \mathbb{W}$? 1 Maximizing the sum of two numbers, the sum of whose squares is constant

# 16 Tags

 2 algebra-precalculus × 4 1 optimization 1 elementary-number-theory × 3 0 arithmetic × 2 1 calculus × 3 0 geometric-construction × 2 1 inequality × 2 0 geometry × 2 1 combinatorics 0 number-theory × 2

# 3 Accounts

 Mathematics 429 rep 412 Stack Overflow 164 rep 13 Super User 128 rep 3