Math puzzle <3

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Across
  1. 2. something that is formed by two rays with a common end point
  2. 4. a vertical line on a coordinate plane
  3. 5. a horizontal line on a coordinate plane
  4. 7. when a point dose not pass through the origin
  5. 10. when x is loyal and dose not have more than one y
  6. 13. infinitely straight lines that do not cross at any point
  7. 15. the formula for slope
  8. 16. the process or breaking a number into equal parts
  9. 19. the middle number
  10. 20. the average
  11. 21. numbers numbers starting from 0(0,1,2,3, etc.)
Down
  1. 1. A vertical and/or slide/shift
  2. 3. the sum of two or more numbers
  3. 6. a shape with three sides
  4. 8. a place value name one spot behind the decimal
  5. 9. a angle that measure less that 90 degrees
  6. 11. the measure of a three dimensional space
  7. 12. When a point passes through the origin
  8. 14. the number repeated the most
  9. 17. a three dimensional circle
  10. 18. the act of taking one number away from a number