Question

A family goes on a long car trip. The number of miles, y, they have left to drive is given by the equation y=510−60x, where x represents the time in hours. Which of the following values could be in the domain in this problem? Check all that apply.

1.5

10

0

60

-3

Answer 1

1.5 and 0

Explanation:

The domain is the set of all possible x-values that make the function work and generate real y-values.

y = 510 – 60x

y cannot be greater than 510, because that would mean they are not yet at their starting point.

y cannot be less than 0, because that would mean they have passed their destination

We can get an idea of the domain if we solve the function for x. We get

x=(510 – y)/60

If y = 510, x = 0.

If y = 0, x = 510/60 = 8.5.

Thus, the domain is 0 ≤ x ≤ 8.5.

The only numbers in your list that could be in the domain are 1.5 and 0.

10 and 60 are wrong, because they give negative values for y.

-3 is wrong, because it gives y > 510.

Answer 2

0,1.5

Explanation:

y = 510 - 60x

We want to find the domain or the x values where x represents the time

We need to determine the possible values for x

Y cannot be greater than 510 or less than 0. 510 means they have not started the trip, and 0 means they have arrived

510 = 510 -60x

Subtract 510 from each side

510-510 = 60x

0 = 60x

The smallest value of x can be 0

0 = 510 - 60x

Subtract 510 from each side

-510 = 510-510-60x

-510=-60x

Divide by -60

-510/-60 = -60x/-60

8.5 = x

The maximum value of x is 8.5 hours

So x must be between 0 and 8.5 inclusive.