Using the product rule, we have
so that
The equation of the tangent line to <em>W(x)</em> at <em>x</em> = 7 has all the information we need to determine <em>m'</em> (7).
When <em>x</em> = 7, the tangent line intersects with the graph of <em>W(x)</em>, and
<em>y</em> = 4.5 + 2 (7 - 7) ==> <em>y</em> = 4.5
means that this intersection occurs at the point (7, 4.5), and this in turn means <em>W</em> (7) = 4.5.
The slope of this tangent line is 2, so <em>W'</em> (7) = 2.
Then
Given :
Ruth wants to buy a skateboard for $44.
She has $100 in her account. She spent $11.36 to buy stationary.
She also wants to buy some comic books for $3.72 each.
To Find :
The maximum number of comic books, n, that Ruth can buy so that she has enough money left to buy the skateboard.
Solution :
Money left after buying skateboard and stationary is :
Money left = $(100 - 11.36 - 44)
Money left = $44.64
Number of comic she can buy is :
Therefore, she can buy a maximum of 12 books.
Hence, this is the required solution.