Mathematics High School

While attempting to multiply the expression (2-5i)(5+2i) a student made a mistake.

(2-5i)(5+2i)= 10+4i -25i - 10i^2
=10+4(-1)-25(-1) - 10(1)
=10-4+25-10
=21
What is the error?

Answers

Answer 1

Answer:

The left side of the equation is ignored

i is treated as -1, which it is not, it is instead the square root of negative 1.

To solve it properly we get:

(2 - 5i)(5 + 2i)

= 10 + 4i - 25i - 10i²

= 10 + 21i + 10

= 20 - 21i

Answer 2

Answer:

The error is that, the student replaced i with -1 which is wrong as i = √-1

And he has replaced i^2 with 1 while i^2 = -1

Step-by-step explanation:

Given two numbers that are being multiplied are:

(2-5i)(5+2i)

We will solve the question to get the right result so that the error can be detected.

So, multiplying both

[tex]= 2(5+2i)-5i(5+2i)\\=10+4i-25i-10i^2\\=10-21i-10(-1)\ \ \ as\ i^2 = -1\\=10-21i+10[/tex]

The error is that, the student replaced i with -1 which is wrong as i = √-1

And he has replaced i^2 with 1 while i^2 = -1

Related Questions

Which expression is equivalent to 45a+23b+18−76b−34−25a?
65a−12b−58
65a+116b+78
25a−12b−58
25a+116b+78

Answers

45a + 23b + 18 - 76b - 34 - 25a
= (Now, we will combine and group the like terms.)
= 45a - 25a + 23b - 76b + 18 - 34
= 20a - 53b - 16.
So, in conclusion, the answer to this question is 20a - 53b - 16 however, none of these answered provided are correct.

You spent $60 in supplies to sell shirts. You sell your shirts for $10
each. How many do you have to sell to make a profit?

Answers

Answer: Atleast 7

Step-by-step explanation:

In order to make a profit you have to amke more money than what you spent for supplies. So if each shirt is 10$ then you would have to sell atleast 7 shirts since if you do you will have made 70$, therefore a 10$ profit. If you sell 6 shirts, you make 60$, meaning you gain all your money back, but you do not make a profit.

the answer is 7

Step-by-step explanation:

7×10=70-60=10

a wish tank that is full of water has sprung a leak, 12% of the water is lost every hour. what % of water is left in the tank after 20 minutes

Answers

96% of the water is still in the tank after 20 minutes.
12% is lost every hour but 20 minutes is 1/3 of an hour so you multiply 12 by 1/3 and you get 4% and at the beginning the water tank is full at 100% so you subtract 100%-4%=96%.

Given that
5
x
:
9
=
8
:
3
Calculate the value of
x
.
THE CORRECT ANSWER WILL BE BRAINLIEST

Answers

Answer:

x=4.8

Step-by-step explanation:

5x:9 = 8:3

It can also be written as

5x/9 = 8/3

Cross multiply

5x*3 = 8*9

15x = 72

Divide both sides by 15

15x/15 = 72/15

x =4.8

i will give brainlist to who ever gets it right

Answers

Answer:

2(j+2)

Step-by-step explanation:

Since 2 is the GCF, you should take out 2 to make the answer 2(j + 2).

Answer:

that will be 2(j+2) by taking hCf outside

plz mark as brainliest

Help me with this thing thanks anoarefi

Answers

Answer:

1. 8

2. 16

Step-by-step explanation:

8/4=2

64/4=16

Answer:

The answers are

1. x=8

2. x=16

PLEASE HELP I HAVE LESS THAN 45 MINUTES! WILL GIVE BRAINLIEST!

Answers

Answer:

5

Step-by-step explanation:

Is this congruent, or not congruent? And is it
SSS
SAS
SSA
AAS
ASA
HL

Answers

Answer:

Step-by-step explanation:

The two triangles are congruent. The diagonal is equal to itself in both triangles.

Triangle XYW = Triangle XYZ  by SSS

Solve 3(−3−3x)+4=−5.

Answers

Answer:

49

Step-by-step explanation:

you need to multiply all them and get 49

Answer:

0

Step-by-step explanation:

3(-3-3x)+4=-5

3(-3-3x)=-9

-9-9x=-9

-9x=0

0/-9=0

If f ( x ) = 2x - 3 and g ( x ) = x 2,

find g ( f ( x ) )
Select one:
a. 4x 2 - 9
b. 4x 2 - 12x + 9
c. 2x 2 - 3

Answers

Answer:

[tex]g(f(x)) = g(2x - 3) = {(2x - 3)}^{2} \\ =\boxed{4 {x}^{2} - 12x + 9}[/tex]

b. is the right answer

Can someone please help me get this answer correct?

Answers

Answer:

I'm pretty sure that would be a rectangle

Step-by-step explanation:

I just graphed it

2.Solve -75 = -25a.
A.
3
B.
-100
c.
-50

Answers

Answer:

A

Step-by-step explanation:

-75=-25a

Divide both sides by -3:

3=a

a=3

The answer is choice A

A sporting goods store manager was selling a ski set for a certain price. The manager offered the markdowns​ shown, making the​ one-day sale price of the ski set ​$323. Find the original selling price of the ski set.

Answers

Answer:
The original selling price is $520.632
Explanation:
Consider the initial selling price be $x
After marking down 10%,
Final Selling price = Selling price(1-10%)
Selling price = x – 10% of x = x – 0.1x = 0.9x
After marking 30%
Final Selling price = Selling price(1-10%)
Selling price = 0.9x – 0.3*0.9x = 0.9x – 0.27x = 0.63x
According to the question,
0.63x = 328

Therefore, the original selling price is $520.632

Answer:

The original selling price is $520.632

Explanation:

Consider the initial selling price be $x

After marking down 10%,

Final Selling price  = Selling price(1-10%)

Selling price = x – 10% of x = x – 0.1x = 0.9x

After marking 30%

Final Selling price  = Selling price(1-10%)

Selling price = 0.9x – 0.3*0.9x = 0.9x – 0.27x = 0.63x

According to the question,

0.63x = 328

Therefore, the original selling price is $520.632

Hope It helps!!❤

PLS help me

this is for class, if you get it right i will give brainliest

Answers

Answer:

Yes

Step-by-step explanation:

a^2+b^2=c^2

7^2+11^2=c^2

49+121=c^2

170=c^2

then square it

c=13

7,11,13 is a pythagorean triple

Answer:

both answers you have put in are correct

Step-by-step explanation:

7^2=49

11^2=121

121+49=170

square root of 170 is the long side

not a pythagorean triple because square root of 170 does not come out as a whole number (no decimal/fraction)

is it ~13.0384

Solve.
12.25 = 2.5 =
4.9
4.5
6.5
0.49

Answers

(If this is the correct symbol)
12.25 divided by 2.5= 4.9

Hope this helps

Have a great day/night

Tank B, which initially contained 80 liters of water, is being drained at a rate of 2.5 liters per minute. How many liters of water remain in the tank after 30 seconds?​

Answers

Answer:

78.75 ?

Step-by-step explanation:

calculator..

The volume of water remain in the tank after 30 seconds is 78.75 liters.

The given parameters;

initial volume of water in Tank B, V₀ = 80 litersrate at which water is being drained, R = 2.5 liters per minute.time of water drain, t = 30 seconds

The amount of water drained after 30 seconds is calculated as follows;

[tex]V_1 =2.5 \ \frac{liters}{\min} \times \frac{1 \min}{60 \ s} \times 30 \ s\\\\V_1 = 1.25 \ liters[/tex]

The volume of water remain in the tank after 30 seconds is calculated as follows;

V₂ = V₀ - V₁

V₂ = 80 liters - 1.25 liters

V₂ = 78.75 liters

Thus, the volume of water remain in the tank after 30 seconds is 78.75 liters.

Learn more here: https://brainly.com/question/13559135

13 more than a number Y is -7.

Answers

Answer:

m

Step-by-step explanation:

j

Answer:

-20

Step-by-step explanation

To make the sentence into an equation it would be y+13=(-17). To solve this you would need to get y by itself. To do this, you would make the equation y+13-13 , since you need to do the same thing from both sides, it would be y+13-13=(-17)-13 . Simplify the equation to make y=(-7)-13 . Counting back 13 from -7 gets you to -20 . Finally you get to  y=(-20) , so the answer is -20

Find the product.
(-7)(5) =

Answers

Answer:

-35

Step-by-step explanation:

Answer:

-35

Step-by-step explanation:

A negative times a positive is a negative number:

-7*5=-35

please help me with this its timed first person to give me correct answer gets 25 points

Answers

Answer:

8. 14 for the third question.

9. 18 for the forth question.

Step-by-step explanation:

the third and forth orange equations.

Find the equation of the circler whose diameter has the end points A( 5,4) and B(7,4)​

Answers

Answer:

(x-a) whole square + (y-b) whole square =r square

you will get answer

Given h(x) = 32
3x – 3, find h(3).

Answers

Answer:

(3×3) - 3 = 6

.

.

.

i didnt get that...wt's that 32?

Please send help ASAP.

Answers

Answer:

d. -4 <= x - 5

Step-by-step explanation:

I think youre asking about question 5.

First replace the x with the -2 in every problem.

Now solve:

a. 6 × -2 < 10

6 times -2 is -12, and -12 is less than -10, so that ones true and not the answer

b. -2 × -2 > -3

-2 times -2 is 4, and 4 is greater than -3, so that ones true and not the answer

c. -2/4 <= 0

-2 divided by 4 is -1/2, and -1/2 is less than 0. so that ones true and not the answer

So obviously the answers d, but we're gonna check anyway

d. -4 <= -2 - 5

-2 minus 5 is -7, and -7 is not less than -4, so its not true and the answer

is (-2+x)-(3x-8) equivalent to -2x+4

Answers

Answer:

No solution

Step-by-step explanation:

There are no values of  x  that make the equation true.

Brainly pls?

Answer:

No, it's not equivalent to it.

Step-by-step explanation:

[tex]( - 2 + x) - (3x - 8) = - 2 + x - 3x + 8 \\ = 6 - 2x = - 2x + 6[/tex]

HELPPPPPPPP ☝️☝️☝️!!!!!!!

Answers

Answer:

10x=y

Step-by-step explanation:

Dividing by 3 is the inverse of multipiying by 3.

Answers

Yes that is indeed correct

An object is accelerating at a constant rate from 8.0 m/s to 16.0 m/s in 10.0 seconds. How far in meters does the object travel in 10.0 seconds?

Answers

Step-by-step explanation:

Answer is 120 m

Extremely sorry for delay.

Here is explanation in given attachment

Simplify -3x^2-5x^2(4x^3-x^2)2

Answers

Let's simplify step-by-step.

−3x2−5x2(4x3−x2)(2)

Distribute:

=−3x2+−40x5+10x4

Answer:

=−40x5+10x4−3x2

Clean123 Inc. performs 1,000 of cleaning services for a customer. After 30 days the computer pays 50% of the invoice with a check. How will this transaction be recorded

Answers

did you get ittttt???

please help me out

Need help with this math question pls help me.

Answers

Answer:

its D

Step-by-step explanation:

You can tell because your trying to find the one that's steeper but you can see that D is pointed a little bit more down than the others

Answer:

It is D because it is the steepest

Step-by-step explanation:

Help me please. Id appreciate it greatly

Answers

Answer:

1.39

2.4/5

3. 4/5t+39

4. 4

5.4/3

6.4/3g+4

i hope i got this right.

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