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Blababa [14]
2 years ago
6

Myra is evaluating the expression –31. 7 4. 5x, when x = 2. 1. -31. 7 4. 5(2. 1) –27. 2(2. 1) –57. 12 What was Myra’s error? Myr

a should have multiplied -31. 7 and 2. 1 first. Myra should have multiplied 4. 5 and 2. 1 first. Myra should have subtracted -27. 2 and 2. 1 first. Myra should have added -31. 7 and 2. 1 first.
Mathematics
1 answer:
murzikaleks [220]2 years ago
4 0

This is just an algebraic problem, the correct option is:

<em>"Myra should have multiplied 4.5 and 2.1 first."</em>

<h3>How to evaluate an expression?</h3>

Here we want to evaluate the expression:

-31.7 + 4.5*x

in x = 2.1

This just means that we need to replace x by 2.1 in the given equation.

Now, what Myra does is:

-31.7 + 4.5*2.1 = -27.2*2.1

So she took the sum between -31.7 and 4.5 first, this is her mistake, you only would do that if the expression was:

(-31.7 + 4.5)*2.1

But in our expression:

-31.7 + 4.5*2.1

The first thing you need to solve is the product in the second term, so we get:

-31.7 + 4.5*2.1 = -31.7 + 9.45 = -22.25

If you want to learn more about algebra, you can read:

brainly.com/question/4344214

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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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Solution : Let the distance of the girl from the street light is = x feet

Length of the shadow CD is = y feet

Therefore, \frac{dx}{dt}=6 feet per sec. [Given]

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

25x - 21x = 21y

4x = 21y

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}

\frac{dw}{dt}=6+1.14

= 7.14 ft per sec.

Therefore, tip of the shadow of the girl is moving with a rate of 7.14 feet per sec.

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Answer:

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Step-by-step explanation:

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-----------------------------------------------

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Making the area to be
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Suppose that y varies inversely as x, and x=9 when y=15. Find the value for k and write the function. Group of answer choices La
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see explanation

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8 0
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