Step-by-step explanation:

The sum of cubes is given as:
a³ + b³ = (a + b)(a² - ab + b²)
Example for the sum of cubes:
64x³+y³ ⇒ This is the sum of cubes because each term; 64, x³, and y³ are cube numbers
By writing each term as an expression of cube numbers, we have:
(4x)³ + (y)³ ⇒ 64 is 4³
Use the factorization of the sum of cubes, we have:
(4x + y) ( (4x)²- 4xy + y²)
(4x + y) (16x² - 4xy + y²)
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The difference of cubes can be factorized as:
(x³ - y³) = (x - y)(x² + xy + y²)
Example
(125x³ - 8y³) = (5x - 2y) ((5x)² + (5x)(2y) + (2y)²)
= (5x - 2y) (25x² + 10xy + 4y²)
Answer: a) 30, b) 0.2138, c) 0.0820
Step-by-step explanation:
Since we have given that
X be the number of calls in 1 hour = 60 minutes
Rate of one call every two minutes.

(a) What is the expected number of 911 calls in one hour?

(b) What is the probability of three 911 calls in five minutes? If required, round your answer to four decimal places.

Number of calls = 3
So, P(X=3) is given by

(c) What is the probability of no 911 calls during a five-minute period? If required, round your answer to four decimal places.

Hence, a) 30, b) 0.2138, c) 0.0820
Answer: It is believed that exactly 20% of Evergreen Valley college students attended the opening night midnight showing of the latest harry potter movie.
Step-by-step explanation:
Since we have given that
n = 84
x = 11
So, 
p = 0.20
So, hypothesis:

so, test statistic value would be

At 1% level of significance, critical value would be
z= 2.58
Since 2.58>-1.604
So, We will accept the null hypothesis.
Hence, It is believed that exactly 20% of Evergreen Valley college students attended the opening night midnight showing of the latest harry potter movie.