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4 days I have 140 copies of a book, 9 days I only have 50 left. Write an equation where c(t)=my+b where c is number of copies still on hand and t days being available.

User Mamoo
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Answer:


c(t)=-18t+212.

Explanation:

We have been given that 4 days I have 140 copies of a book, 9 days I only have 50 left. We are asked to write an equation
c(t)=my+b, where c is number of copies still on hand and t days being available.

We have two points on line (4,140) and (9,50). Now, we will use these points to find slope as:


m=(140-50)/(4-9)


m=(90)/(-5)


m=-18

Now, we will use point-slope form of equation
y-y_1=m(x-x_1) and substitute
m=-18 and coordinates of point (9,50) as:


y-50=-18(x-9)


y-50=-18x+162


y-50+50=-18x+162+50


y=-18x+212

Therefore, our required equation would be
c(t)=-18t+212.

User Sebastian Delgado
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