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SMO 2007 Junior Round 1 Question 10

SMO · SMO 2007 Junior Round 1

Question 10

Suppose $x^2-13x+1=0$. What is the last digit of $x^4+x^{-4}$?
  1. $1$
  2. $3$
  3. $5$
  4. $7$
  5. $9$