5x-8y=1...(1)
3x+6y=-21...(2)
(1)*3:
15x-24y=3...(3)
(2)*5:
15x+30y=-105...(2)
(3)-(2):
15x-24y-(15x+30y)=3-(-105)
15x-24y-15x-30y=108
-54y=108
y=-2
Answer:
(a)
-- Population Mean
(b)
--- Population standard deviation
(c) See Explanation
Step-by-step explanation:
Given:
Cigarette tax for 20 regions
Solving (a): The population mean
This is calculated as:




So, we have:


Solving (b): The population standard deviation
This is calculated as:



So:



Solving (c):
Population mean tells the average amount while the standard deviation represents the spread from the calculated mean
Option (4) is correct
Answer:
c = 0.165
Step-by-step explanation:
Given:
f(x, y) = cx y(1 + y) for 0 ≤ x ≤ 3 and 0 ≤ y ≤ 3,
f(x, y) = 0 otherwise.
Required:
The value of c
To find the value of c, we make use of the property of a joint probability distribution function which states that

where a and b represent -infinity to +infinity (in other words, the bound of the distribution)
By substituting cx y(1 + y) for f(x, y) and replacing a and b with their respective values, we have

Since c is a constant, we can bring it out of the integral sign; to give us

Open the bracket

Integrate with respect to y

Substitute 0 and 3 for y



Add fraction


Rewrite;

The
is a constant, so it can be removed from the integral sign to give


Integrate with respect to x

Substitute 0 and 3 for x




Multiply both sides by 


2(x - 3) + 4y - 2(x - y - 3) + 5 =
2x - 6 + 4y - 2x + 2y + 6 + 5 =
6y + 5 <== ur x terms cancel and ur 6's cancel