Question

Determine c so that f(x,y) satisfies the conditions of being a joint pmf for 2 discrete random variables X and Y
\(f(x,y)=c(\dfrac{1}{4})^x(\dfrac{1}{3})^y\) x = 1, 2,.......
y = 1, 2, ........
Please help

Answer 1

is the answer 33/4 ?

Answer 2

6

Answer 3

http://www.wolframalpha.com/input/?i=%5Csum_%7Bx%3D1%7D%5E%7B%5Cinfty%7D%5Csum_%7By%3D1%7D%5E%7Bx%7D+%28%281%2F4%29%5Ex*%281%2F3%29%5Ey%29

Answer 4

pmf meaning?

Answer 5

probability mass function

Answer 6

@ganeshie8 I see nothing on the wolfram , Is there something wrong?

Answer 7

so integral of the volume under the surface f(x,y) =1

Answer 8

@dan815 no, this is discrete, not continuous. We use sum, not integral

Answer 9

try entering below

```
\sum_{x=1}^{\infty}\sum_{y=1}^{x} ((1/4)^x*(1/3)^y)
```

Answer 10

well then trapezoid or cubes under the surface approximation then

Answer 11

@ganeshie8 problem 4_1_1 d)