Use A Calculator. They are Good Espically those chocolated smelled ones. :)
Plug in any value for x and then you will get y. Use the coordinates to plot.
Example
x= 2
5/2(2)-6
5-6
-1
(2,-1)
Then continue to do the same.
The event that either M1 or M2 fails has probability

by the addition rule. Failure events are independent, so

so that

Denote this probability by
. Then
follows a geometric distribution with this parameter
and has density

The expectation is
.