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Delicious77 [7]

4 years ago

7

A library is having a book sale to raise money. Hard cover books cost $4 each and paperback books cost $2 each. A person spends

$26 for eight books. How many hard cover books did she purchase?

1 answer:

Crank4 years ago

4 0

I don't really know how to explain, but I will give you the straight up answer

5 HARDCOVER BOOKS (would total up to $20)
3 paperback books (would total up to $6)

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Suppose that a Petri dish initially contains 2000 bacteria cells. An antibiotic is introduced and after 4 hour, there are now 16

Sergeu [11.5K]

Answer:

a)The linear function for $P(t)$ is:

$P(t) = 2000 - 100*t$

b)The exponential function for $P(t)$ is:

$P(t) = 2000e^{-0.055t}$

Step-by-step explanation:

(a) Suppose that P(t) is a linear function. Find a formula for P(t):

$P(t)$ can be modeled by a linear function in the following format.

$P(t) = P_{0} - r*t$ , in which $P_{0}$ is the initial number of bacteria cells in the dish, t is the time and r is the rate that the number decreases.

Since the dish initially contains 2000 bacteria cells, $P_{0} = 2000$

We have

$P(t) = 2000 - r*t$

An antibiotic is introduced and after 4 hour, there are now 1600 bacteria cells present. So $P(4) = 1600$ . With this information, we can find the value of r.

$P(t) = 2000 - r*t$

$1600 = 2000 - r*(4)$

$4r = 400$

$r = \frac{400}{4}$

$r = 100$

So, the linear function for $P(t)$ is:

$P(t) = 2000 - 100*t$

b) Suppose that P(t) is an exponential function. Find a formula for P(t)

$P(t)$ can also be modeled by an exponential function in the following format:

$P(t) = P_{0}e^{rt}$

The values mean the same as in a). We use the fact that $P(4) = 1600$ to find r.

$P(t) = 2000e^{rt}$

$1600 = 2000e^{4r}$

$e^{4r} = \frac{1600}{2000}$

$e^{4r} = 0.8$

$ln e^{4r} = ln 0.8$

$4r = -0.22$

$r = \frac{-0.22}{4}$

$r = -0.055$

So, the exponential function for $P(t)$ is:

$P(t) = 2000e^{-0.055t}$

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Step-by-step explanation:

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Answer:

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Step-by-step explanation:

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Area of a circle:

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