b Substitute the given value into the equation for t.
A
aDependent Variable: y Independent Variable: x
B
b Domain: 0≤ x ≤4
Range: 100≤ y ≤ 140
Practice makes perfect
a Since the amount y of money in your bank account depends on the number x of hours for which you babysit, we can identify y as the dependent variable and x is the independent variable.
b The minimum number of minutes for which we can work is 0. To determine the amount of money that corresponds with this time, we can substitute x=0 into the equation and solve for y.
The minimum amount of money in the bank account is 100 dollars. Now, let's calculate the maximum amount. To do that, we can substitute x=4 into the equation and solve for y, since 4 is the maximum number of hours we can work.
Since y=140 when x=4, the maximum amount of money in your bank account is 140 dollars. Now we know that we can have from 100 to 140 dollars in the bank account. These values represent the lower and upper boundaries of our domain and range.
Domain:& 0≤ x ≤ 4
Range:& 100≤ y ≤ 140
