# Mistake in expression

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

(2 - 5i)(5 + 2i) = 10 + 4i - 25i - 10i2

= 10 + 4(-1) - 25(-1) - 10(1)

= 10 - 4 + 25 - 10

= 21

Complete the explanation and correct the error.

Hint: The student incorrectly defined i as being equal to ___ instead of ___. The student should have written the product as :

(2 - 5i)(5 + 2i) = 10 + 4i - 25i - 10i2

= 10 + 4(-1) - 25(-1) - 10(1)

= 10 - 4 + 25 - 10

= 21

Complete the explanation and correct the error.

Hint: The student incorrectly defined i as being equal to ___ instead of ___. The student should have written the product as :

### Correct answer:

Tips for related online calculators

Try our complex numbers calculator.

#### You need to know the following knowledge to solve this word math problem:

## Related math problems and questions:

- Pool

If water flows into the pool by two inlets, fill the whole for 19 hours. The first inlet filled the pool 5 hour longer than the second. How long does the pool take to fill with two inlets separately? - Evaluate with brackets

Find the Error - tell what the mistake is 6[(4 + 9) - 32] ÷ 2 6[13-32]÷2 6[13-9]÷2 6[9]÷2 6[4.5] 27 - Danny

Danny made a mistake in the following problem. Line 1:21 + 35 ÷ 7 + 6(2) Line 2:21 + 5 + 6(2) Line 3:21 + 11(2) Line 4:21 + 22 Line 5:43 On what line was the mistake made? Only input the number of the first incorrect line. - Describe 11

Describe and correct the error in finding the difference function of (f-g) (x) of f(x) =(x²+3x-1) and g(x) =(x²+x+2) (f-g) (x) =f(x)-g(x) =(x²+3x-1) - (x²+x+2) =x²+3x-1 -x²+x+2 =x²-x²+3x+x-1+2 =4x+1 - Find the 5

Find the equation of the circle with the center at (1,20), which touches the line 8x+5y-19=0 - Mistake

Nicol needs to correct errors when calculating in school. Instead of adding the number 20, she subtracts it. What is the difference between the result and the correct result? - Test points

A test has 20 questions. The test awards 3 points if the answer is correct and takes away 1 point if the answer is incorrect. A student answered five questions incorrectly. How many points did the student earn? - Linear system

Solve this linear system (two linear equations with two unknowns): x+y =36 19x+22y=720 - Find error in calculation

Sally's calculations are as follows 39-9×4+12 =30×16 =480 What are the errors in this calculation? - Solve 24

Solve the following equation, answer as a reduced, mixed number. Then place the correct number in the box provided. 4(2x -3) + 8(x - 4) = 2(2x + 6) - A group

A group of young men decides to raise ksh 480,000 to start a business. Before the actual payment was made, four members pulled out, and each of the remaining had to pay an additional ksh 20,000. Determine the original number of members. - Frustum of a cone

A reservoir contains 28.54 m³ of water when complete. The diameter of the upper base is 3.5 m, while the lower base is 2.5 m. Find the height if the reservoir is in the form of a frustum of a right circular cone. - Expression

If A=2 B=3, evaluate expression A(B+A) and multiply it by A - Small and large bread

Kipton's aunt bakes a large loaf of bread and a small loaf of bread. She cuts each loaf into tenths and gives Kipton 2 tenths of each loaf to take home. Kipton writes the equation 2/10 + 2/10 = 4/10 to show the amount of bread he takes home. Explain Kipto - PLUS MINUS product

A. Deduct 15.728 from the sum of 23.234 and 6.23 B. Add 15.756 to the difference of 26.845 and 4.342 C. Find the product of 0.86 x 0.05 D. Multiply 5.234 by 4.45 E What is the product of 23.97 multiplied by 6.36? - Pass a test

The student has to pass a test that contains ten questions. For each of them, he chooses one of 5 answers, with just one being correct. The student did not prepare for the test, so he randomly chose the answers. What are the probabilities that the student - Adding denominators

Max is working out 2/3+7/9. He says the answer is 9/12. What mistake has Max made?