Please explain this
(1+2i) (1-2i)

Step-by-step explanation:

f: 1 * 1 = 1

o: 1 * - 2i

i: 2i * 1

l: 2i * - 2i = - 4i^2 = -4 * i^2 = -4 * -1 = 4

Answer

1 - 2i + 2i + 4

5

(1+2i) · (1-2i) - Start with the given expression.

(1) · (1) · (1) · (-2i) + (2i) · (1) + (2i) · (-2i) - FOIL.

1 - 2i + 2i - 4i² - Multiply.

1 - 2i + 2i - 4 · (-1) - Replace i²  with -1. - Note: i² = -1

1 - 2i + 2i + 4 - Multiply.

5 + 0i - Combine like terms.

5 - Simplify

So (1 + 2i) · (1-2i) = 5.

The expression is now in standard form  a + bi where  a =5 and b = 0

percentage - 25%

probability - 0.25

we know,

total amount of students in class = 20

total boys = 10

total girls = 10

no of girls who wear glasses = 10/2 = 5

probability of choosing a girl with glasses is =

number of girls wearing glasses/total number of students in the class = 5/20

thus, percentage of selecting a girl wearing glasses will be

= 5/20 × 100

= 5 × 5

25%

therefore,

probability will be 0.25

happy to

pls mark as brainliest

54 kilometers per hour

step-by-step explanation:

according to rules:

1 km = 1000 meter

which means that 1 meter = 1/1000 km

1 hour = 3600 second [ as 1 hour = 60 min = 60 *60 seconds ]

which means that 1 second = 1/3600 hour

therefore, 1 kilometer/hour =

thus to convert 15 meter per second to kilometer per hour, we multiply 15 to 3.6 kilometer/hour.

15 meter/second=   which is the required answer.