Question

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.

Answer 1

Answer:

$c(t)=-18t+212$.

Step-by-step 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:

$m=\frac{140-50}{4-9}$

$m=\frac{90}{-5}$

$m=-18$

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 $c(t)=-18t+212$.