discrete probability function P(X=i) =(1/2)^i for i = 1,2,3 X³ e [-9,9]

[Mohojojo]

Hello there, perhaps you can help me.
The first task is, to calculate the probability in Range of
My gues is that only for i=1 and i=2 is X in Range, cause of 1² < 9 and 2² < 9.
The probabilty is (1/2)^1 + (1/2)^2 = 0.75 then.

In the second task you should find a 0,2-quantile of the function. And it have to be i=1, cause its allready
p=0,5.

I think my solutions are to simple, so i have to be wrong. Can you help me with my thought process ?
LG Mohojojo

 

[Dason]

Nothing is bad about simple solution when the problems aren't complex.