You can solve this by algebraically as well as graphically. When I tried both ways I got:
solution is x= -2<span />
The exponential distribution is:

where

The probability we want is how likely will a dvd player last more than 8 years, given it has already lasted 5 years
To find this, you use conditional probability.

where A is P(x>8) and B is P(x>5)
To find these probabilities, integrate over the distribution:

Sub into conditional probability formula:

Final Answer: Given a dvd player is more than 5 years old, the probability that it will last another 3 more years is about 54.9%
Answer:
n = 0, n =2
Step-by-step explanation:
Given
(n + 1) + 3(n - 1) = 2(n - 1)(n + 1) ← distribute parenthesis on both sides
n + 1 + 3n - 3 = 2(n² - 1), that is
4n - 2 = 2n² - 2 ( subtract 4n - 2 from both sides )
0 = 2n² - 4n ← factor out 2n from each term )
0 = 2n(n - 2)
Equate each factor to zero and solve for n
2n = 0 ⇒ n = 0
n - 2 = 0 ⇒ n = 2