100 points <br> answer asap

Let $a$ and $b$ be nonzero real numbers such that

algol [13]

<h3>Answer: -7/2</h3>

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Explanation:

Let's expand out (2 - 7i)(a + bi) using the FOIL rule

(2 - 7i)(a + bi) = 2a + 2bi - 7ai - 7bi^2

(2 - 7i)(a + bi) = 2a + 2bi - 7ai - 7b(-1)

(2 - 7i)(a + bi) = 2a + 2bi - 7ai + 7b

(2 - 7i)(a + bi) = (2a+7b) + (2bi-7ai)

(2 - 7i)(a + bi) = (2a+7b) + (2b-7a)i

We're told the result is purely imaginary. What this means is that the real part (2a+7b) is zero, while the imaginary part (2b-7a) is nonzero. If both are zero, then we have 0+0i = 0 which is purely real.

For example, the complex numbers 0-7i and 0+2i are purely imaginary.

Let's use the fact that 2a+7b must be zero to do the following steps:

2a+7b = 0

2a = -7b

a = -7b/2

a/b = -7/2 which is the final answer

We must check to see if 2b-7a is nonzero

2b - 7a = 2b - 7(-7b/2)

2b - 7a = 2b + 24.5b

2b - 7a = 26.5b

The result is nonzero if and only if b is nonzero. Luckily we're told b is nonzero at the top of the problem. So we don't have any worries that (2b-7a) is zero.

Therefore, (2a+7b) + (2b-7a)i will be purely imaginary with a/b = -7/2

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A concrete example:

Let a = -14 and b = 4

a/b = -14/4 = -7/2

(2-7i)(a+bi) = (2-7i)(-14+4i) = 0 + 106i which is purely imaginary.

I'll let you do the steps in expanding that out using the FOIL rule.

4 0

1 year ago

Please help me find x

Ghella [55]

Answer:

x = 53

Step-by-step explanation:

Remember that the sum of all 3 interior angles in a triangle is 180∘ so

74 + x + x = 180

74 + 2x = 180

2x = 180 - 74

2x = 106

x = 106/2

x = 53

3 0

3 years ago

Read 2 more answers

Let g(x) = 2x2 - 11x. Find g(-1).<br> A) -13 Eliminate <br> B) -9 <br> C) 0 <br> D) 13

worty [1.4K]

Solution

g(x) = 2 $x^{2}$ - 11x

Plugging in x = -1 in g(x), we get

g(-1) = 2 $(-1)^{2}$ - 11(-1)

Now we have to simplify it.

g(-1) = 2*1 + 11

g(-1) = 2 + 11

g(-1) = 13

So the answer is D) 13.

Thank you. :)

3 0

3 years ago

Vocabulary Choose the example of an inverse relationship.

natulia [17]

Answer:

which statement is equivalent to the inequality 14x-14>-7x+7

x>21

x>1

x<