Across
1
Number less than zero
4
Reference line in a graph
5
Line touching circle at one point
7
Rectangular array of numbers
9
Steepness of a line
Down
2
Difference between highest and lowest values
3
U-shaped curve of a quadratic function
4
Math using letters for unknown values
6
Symbol representing unknown value
7
Repeated addition
8
Value that does not change
10
The number representing nothing