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ITMC 2018 Grade 9 National Preliminary set01 Question 15

ITMC · ITMC 2018 Grade 9 National Preliminary set01

Question 15

Let real $x$ satisfy $\sqrt{x+30}+\sqrt{x-30}=20$. Find $\sqrt{x+30}-\sqrt{x-30}$.
  1. $-\sqrt{20}$
  2. $-3$
  3. $1$
  4. $3$
  5. $\sqrt{20}$