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3 years ago

6

A phone was purchased for $318. Each year the value is 1/2 of its value the previous year. Write a function that describes the v

alue of the phone, in dollars, as a function of the time in years,t, after the initial purchase?

1 answer:

zubka84 [21]3 years ago

8 0

Answer:

y=318(1-0.5)^x

Step-by-step explanation:

x represents the amount of years and y is the ending price

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The work of a student to find the dimensions of a rectangle of area 8 + 16x and width 4 is shown below:

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Answer:

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2 years ago

A street light is at the top of a 25 ft pole. A 4 ft tall girl walks along a straight path away from the pole with a speed of 6

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Answer:

Tip of the shadow of the girl is moving with a rate of 7.14 feet per sec.

Step-by-step explanation:

Given : In the figure attached, Length of girl EC = 4 ft

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Girl is moving away from the light with a speed = 6 ft per sec.

To Find : Rate ( $\frac{dw}{dt}$ ) of the tip (D) of the girl's shadow (BD) moving away from th

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Length of the shadow CD is = y feet

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In the figure attached, ΔAFE and ΔADE are similar.

By the property of similar triangles,

$\frac{x}{21}=\frac{x+y}{25}$

25x = 21(x + y)

25x = 21x + 21y

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y = $\frac{4x}{21}$

Now we take the derivative on both the sides,

$\frac{dy}{dt}=\frac{4}{21}\times \frac{dx}{dt}$

= $\frac{4}{21}\times 6$

= $\frac{8}{7}$

≈ 1.14 ft per sec.

Since w = x + y

Therefore, $\frac{dw}{dt}= \frac{dx}{dt}+\frac{dy}{dt}$

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= 7.14 ft per sec.

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