This is the input/output table for a linear function. Linear functions increase or decrease by a constant value (the slope).
(38 - 19) / (2 -1) = 19
See how every output is +19 the one before it?
then the output following 57 is 57+19 = 76
1 is one 19
2 is two 19's
3 is three 19's
n is 19n
it is a rational number because it can be written as a fraction
