Answer:
x = -3, 6
Step-by-step explanation:
First, add 18 to both sides
x² - 3x - 18 = 0
+ 18 + 18
x² - 3x = 18
Add 9/4 to both sides because that is the square of half of -3
x² - 3x + 9/4 = 18 + 9/4
Multiply both sides by 4 to get rid of the fractions
(x² - 3x + 9/4 = 18 + 9/4)4
4x² - 12x + 9 = 72 + 9 = 81
Factor the left side of the equation
(2x - 3)² = 81
√(2x - 3)² = √81
Because of the square root, this will result in a positive number and a negative number
2x - 3 = 9
2x - 3 = -9
For both equations, add 3 to both sides then divide by 2
2x - 3 = 9
+ 3 +3
2x = 12
2x/2 = 12/2
x = 6
2x - 3 = -9
+ 3 + 3
2x = -6
x = -3
Answer:
x=-1/85; y=-283/85; z=2/17
Step-by-step explanation:
Using an algebraic method like elimination or substitution would take a lot of steps which could lead to mistake the calculations. In this case, I decided to use the Gaussian elimination. We can express the system in matrix form as follows:
![\left[\begin{array}{ccc}2&-4&6\\9&-3&1\\5&0&9\end{array}\right] \left[\begin{array}{ccc}x\\y\\z\end{array}\right] =\left[\begin{array}{ccc}14\\10\\1\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D2%26-4%266%5C%5C9%26-3%261%5C%5C5%260%269%5Cend%7Barray%7D%5Cright%5D%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7Dx%5C%5Cy%5C%5Cz%5Cend%7Barray%7D%5Cright%5D%20%3D%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D14%5C%5C10%5C%5C1%5Cend%7Barray%7D%5Cright%5D)
To begin the calculations, we write the system in augmented matrix form and use the Gaussian elimination:
![\left[\begin{array}{ccccc}2&-4&6&|&14\\9&-3&1&|&10\\5&0&9&|&1\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D2%26-4%266%26%7C%2614%5C%5C9%26-3%261%26%7C%2610%5C%5C5%260%269%26%7C%261%5Cend%7Barray%7D%5Cright%5D)
By applying the Gaussian elimination, the final matrix is the following:
![\left[\begin{array}{ccccc}1&0&0&|&-1/85\\0&1&0&|&-283/85\\0&0&1&|&2/17\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccccc%7D1%260%260%26%7C%26-1%2F85%5C%5C0%261%260%26%7C%26-283%2F85%5C%5C0%260%261%26%7C%262%2F17%5Cend%7Barray%7D%5Cright%5D)
In order to verify the results, it´s enough to substitute the calculated values in the original equations to see if the equalities are correct. Here you can see the verification for all of the equations:

Answer:
0.381 is the probability that the number of drivers will be at most 18.
Step-by-step explanation:
We are given the following information in the question:
The number of drivers who travel between a particular origin and destination during a designated time period has a Poisson distribution with parameter μ = 20.
- The Poisson distribution is the discrete probability distribution of the number of events occurring in a given time period, given the average number of times the event occurs over that time period.
- The variance of Poisson distribution is equal to the mean of Poisson distribution.
a) P(number of drivers will be at most 18)
Formula:


Thus, 0.381 is the probability that the number of drivers will be at most 18.
10008 hours per 3 years is average of 3336 hours per year, or about 9.1 per day.