Can someone help with me this pls

a) The class interval containing the median is the interval 2 ≤ h <  3

b) The mean number of hours the children spent on their tablets is 2.2 hours.

Step-by-step explanation:

a) The given parameters are;

The number of students that spent 0 ≤ h < 1 hour = 4

The number of students that spent 1 ≤ h < 2 hours = 8

The number of students that spent 2 ≤ h < 3 hours = 11

The number of students that spent 3 ≤ h < 4 hours = 7

The median is given by the location of the 15th child which is located in the interval given as follows;

We note that the total number of children is obtained by adding the  frequencies of the intervals together, as follows;

The number of children = 4 + 8 + 11 + 7 = 30

The frequency of the first interval = 4

The sum of the first + Second intervals = 4 + 8 = 12

The sum of the first + Second + Third intervals = 4 + 8 + 11 = 23

Therefore, the class interval containing the median is the interval 2 ≤ h <  3

b) We use the midpoint of each class interval to find the mean as follows;

The mean = ∑fh/∑h

∴ The mean = (4 × 0.5 + 8 × 1.5 + 11 × 2.5 + 7 × 3.5)/(4 + 8 + 11 + 7) = 2.2

The mean number of hours the children spent on their tablets = 2.2 hours.

the answer to your question is b.

x^2 + 81

we can factor this using difference of square binomials.

rewrite the equation:

x^2 - (-81)

factor:

(a^2 - b^2) = (√a^2 + √b^2)(√a^2 - √b^2)

(x^2 - (-81) = (x + √-81)(x - √-81)

we can remove the - from under the radical by multiplying it by i.

(x^2 - (-81) = (x + i√81)(x - i√81)

(x^2 - (-81) = (x + 9i)(x - 9i)

we can check our answer by using foil:

x^2 - 9ix + 9ix - 81i^2

x^2 - 81^2

i^2 = -1

x^2 + 81