X Y 1st differences
0 -1
1-(-1)=1+1=2
1 1
3-1=2
2 3
5-3=2
3 5
7-5=2
4 7
Since the FIRST differences are all the same -- that is, they
are all 2's, the data is of a FIRST degree polynomial, which
means it is linear, and follows the linear or FIRST DEGREE
equation
y = 2x - 1
Edwin