we have the equation
xy=20
where
y ----> is the time in hours
x ----> is the speed in miles per hours
so
y=20/x
using a graphing tool
The domain ---> Remember that the denominator cannot be equal to zero
so
x>0
The range
The graph has a vertical asymptote at x=0 and a horizontal asymptote at y=0
so
The range is the interval (0, infinite)
therefore