Question

1.3.15

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The monthly water bill is a function of the number of gallons used. The cost is $15.50 for 15,000 gal or less. Over 15,000 gal, the cost is $15.50 plus $1 for each
1000 gal over 15,000 with any fraction of 1000 gal charged at a fraction of $1. On what interval is the cost constant? On what interval is the cost increasing?

Answer 1

The interval in which the cost is constant is

[0,15000]

Explanation:

The interval is increasing by [1500,∞]

Answer 2

The interval over which the cost is constant is from >0 to 15,000 gallons

The interval for which the the cost is increasing is from above 15,000 gallons

Explanation:

For 15,000 gal or less the cost of the monthly water bill = $15.50

For over 15,000 gal, the cost of the monthly water bill = $15.50 plus $1 for each 1000 gal over 15,000 with any fraction of $1,000 charged at a fraction of $1

The interval for which the cost is constant is from 0 ≤ x ≤ 15,000 gal

The interval over which the const is increasing per 1000 gal over 15,000 gallons is from x > 15,000 gal.