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
.
Answer:
x = -30
Step-by-step explanation:
subtract 7 from both sides ( 7+2/5x -7, -5-7 )
simplify ( 2/5x = 12 )
multiply both sides by 5 ( 2/5x times 5 = 5 (-12) )
simplify ( 2x = -60 )
divide both sides by 2 ( 2x / 2, -60 / 2 )
x = -30
Answer:

Graph in the image attached.
Step-by-step explanation:
Using the model of a linear equation, we have:

'b' is the y-intercept of the equation, that is, the inicial value of G, when D = 0.
So if David starts the trip with 14 gallons of gas, we have b = 14.
'a' is the slope of the line, that is, an increase of 1 in the value of D causes an increase of 'a' in the value of G.
So if the car uses one gallon every 20 miles, the value of a is -1/20 (an increase of 20 in D causes a decrease of 1 in G).]
So our equation is:

The graph of this equation is in the image attached.