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4 years ago

10

Evaluate the expression ( 1 + 2 i ) ( − 2 − 1 i ) and write the result in the form a + b i .

1 answer:

Nina [5.8K]4 years ago

6 0

Answer:

- 5i.

Step-by-step explanation:

( 1 + 2 i ) ( − 2 − 1 i )

= 1 * -2 + 1*-1i + 2i*-2 - 2i*1i

= -2 - i - 4i - 2i^2 i^2 = -1 so we have:

-2 - 5i +2

= 0 - 5i

= -5i.

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sashaice [31]

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6/35
The other way which most likely I think you should choose this way is D why?? Because there are out of the red are 3 out of 7 rows that are combined with blue and 2 out of 5 of the blue column are combined with red This makes the 3/7×2/5 = with the 6/35 (combined colors/total)

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3 years ago

HELP DUE IN 10 MINS!

Scilla [17]

Answer:

$\checkmark \text{B. The area of the circle is } 729\pi,\\\checkmark \text{D. The arc length of the sector is } 12\pi$

Step-by-step explanation:

Area of a circle with radius $r$ : $r^2\pi$

Circumference of a sector with radius $r$ : $2r\pi$

Area of sector with angle $\theta$ : $r^2\pi\cdot \frac{\theta}{360}$ .

Arc length of sector with angle $\theta$ : $2r\pi\cdot \frac{\theta}{360}$

Using these equations, we get the following information:

Area of circle: $27^2\pi=729\pi$

Circumference of a circle: $2\cdot 27\cdot \pi=54\pi$

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Arc length of sector: $2\cdot 27\cdot \pi \cdot \frac{80}{360}=12\pi$

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3 years ago

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natulia [17]

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3 years ago

What is the value of the fourth power of 10

Shalnov [3]

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3 years ago

Read 2 more answers

Part A: Joel uses the incorrect expression 0.95(190)(0.8) to calculate that the computer will cost him a total of $144.40. Descr

notka56 [123]

Answer:

Part A) The correct Expression : (1.05)(190)(0.8)

=> The error of Joel was that instead of adding the sales tax, he subtracted it.

Part B) $159.60

Step-by-step explanation:

<u><em>Part A:</em></u>

To calculate the computer cost, we need to find out the selling price first.

There's a discount of 20% so the selling price will be 100% - 20% = 80% =>80/100 = 0.8

<em>So, We'll multiply the cost price by 0.8</em>

=> (190)(0.8)

But, there is a sales tax of 5%

<u><em>So, the selling price with cost price will be:</em></u>

=> 100% + 5% = 105% => 105/100 = 1.05 (We'll multiply this too with the first equation that we made above)

So, the expression will be:

=> (1.05)(190)(0.8)

The error of Joel was that instead of adding the sales tax, he subtracted it.

<u><em>Part B)</em></u>

<u><em>Joel will pay for the tablet:</em></u>

=> (1.05)(190)(0.8) [We used the above expression]

=> $159.60

6 0

3 years ago