A linear graph is one where there is a steady change in the value on the y-axis with a steady change in the value on the x-axis. The first table will produce a positive sloped straight line that has an increase of 5 in the value of distance with each increment in the time value. Table 2 will produce a graph where there is a decrease of 2 in the value of distance with an increase in the value of time. Table 4 will produce a graph where the line is horizontal; the y-value does not change with time.
Table 3 has a graph which has to move up and down to accommodate the decreasing and increasing values, so it will be non-linear.
