Answer:
it's 2
Step-by-step explanation:
8/4= 2
4/2= 2
therefore, the commom ratio of the sequence is 2
D I think because 18 divided by 3 would give you 6 which is the same amount you ran in 1 he
The answer is -5/4
If you want the steps, just ask me in the comments. I hope this helps!
We obtain the joint PMF directly from the joint MGF:

![\implies\mathrm{Pr}[X=x,Y=y]=\begin{cases}0.1&\text{for }x=y=0\\0.2&\text{for }x=1,y=0\\0.3&\text{for }x=0,y=1\\0.4&\text{for }x=y=1\\0&\text{otherwise}\end{cases}](https://tex.z-dn.net/?f=%5Cimplies%5Cmathrm%7BPr%7D%5BX%3Dx%2CY%3Dy%5D%3D%5Cbegin%7Bcases%7D0.1%26%5Ctext%7Bfor%20%7Dx%3Dy%3D0%5C%5C0.2%26%5Ctext%7Bfor%20%7Dx%3D1%2Cy%3D0%5C%5C0.3%26%5Ctext%7Bfor%20%7Dx%3D0%2Cy%3D1%5C%5C0.4%26%5Ctext%7Bfor%20%7Dx%3Dy%3D1%5C%5C0%26%5Ctext%7Botherwise%7D%5Cend%7Bcases%7D)
Then
![\mathrm{Pr}[X=Y]=\mathrm{Pr}[X=Y=0]+\mathrm{Pr}[X=Y=1]=0.1+0.4=\boxed{0.5}](https://tex.z-dn.net/?f=%5Cmathrm%7BPr%7D%5BX%3DY%5D%3D%5Cmathrm%7BPr%7D%5BX%3DY%3D0%5D%2B%5Cmathrm%7BPr%7D%5BX%3DY%3D1%5D%3D0.1%2B0.4%3D%5Cboxed%7B0.5%7D)