Example
Paolo is going to take part in a 20-kilometer walk.
He makes this graph to show the relationship
between time and remaining distance if he
maintains his planned speed. Write an equation
for this function.
Make a table to
xo123 45
find the slope and
y 2016 12 8 40
the y-intercept.
Distance
Remaining (km)
0
1
2 3 4 5
Time (hr)
The table shows that when x = 0, y = 20, so the y-intercept is
20. As each x-coordinate increases by 1, each y-coordinate
decreases by 4, so the slope is 4, or-4.
The equation is y = - 4x + 20.

1 What do the y-intercept and the slope mean in the
context of the example problem?