Timothy's Crossword puzzle

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Across
  1. 2. slope of a horizontal line
  2. 4. polynomial with two terms
  3. 9. most often
  4. 10. middle number in a set of data
  5. 11. The answer to division
  6. 12. is the same as minus
  7. 14. formula is y-y over x-x
  8. 15. average of data
Down
  1. 1. is the "x" on an axis
  2. 3. to add
  3. 5. A+(B+C)=(A+B)+C
  4. 6. the answer to multiplication
  5. 7. A=A
  6. 8. Slope of a vertical line
  7. 9. polynomial with one term
  8. 13. is "y" on an axis