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IMAS 2019–2020 Junior Division — First Round Question 18

IMAS · IMAS 2019–2020 Junior Division — First Round

Question 18

Given that $x=\sqrt{19-8\sqrt3}$, which of the following equalities holds true?
  1. $x^2=11$
  2. $x^2+8x=13$
  3. $x^2-8x=-13$
  4. $x^2+4x=8$
  5. $x^2-4x=-8$