Grace's Crossword

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Across
  1. 4. numbers that appear most in a set of numbers
  2. 5. 3xy
  3. 6. middle value of number in set of numbers
  4. 9. expression involving variables
Down
  1. 1. consisting of several terms
  2. 2. function f(x) = ax2 + bx + c
  3. 3. value average of several numbers
  4. 7. equality of two expressions
  5. 8. three terms that are connected by plus or minus notations