Let y represent the total cost of publishing a book (in dollars). Let x represent the number of copies of the book printed.

Question

Suppose that x and y are related by the equation.

1150+25x=y

Answer the questions below.

Note that a change can be an increase or a decrease. For an increase, use a positive number. For a decrease, use a negative number.

What is the change in the total cost for each book printed ?

What is the cost to get started ( before any books are printed ) ?

Answer 1

Since y is cost and x are books, you plug in the numbers that each question implies:

First, What is the change in the total cost for each book printed?

Well, we know the equation is linear, so the cost should be the same with each book. Let's plug in 2 numbers, and see how the cost changes:

for 1 book (x = 1)

1150+25(1)= 1175

For 2 books (x - 2)

1150+25(2) = 1200

Next, to find the change in total cost, subtract these 2 answers:

1200 - 1175 = 25

$25.00 is the change in total cost. Notice that this number is also the slope of this linear equation (the term in front of the x.

For the next question: What is the cost to get started ( before any books are printed )?

Well, for that, we set x = 0 since there are no books:

1150+25(0)= 1150

$1150.00 is the startup cost