A research paper recommends using Poisson process to model the number of failures in commercial water pipes The paper also gives estimates the failure rate in units of failures per 100 miles of pipe per day; for four different types of pipe and for many different years_ For example, for cast iron pipe in 2005, the authors' estimate is the failure rate is 0.0864 failures per 100 miles per day: Suppose a town had 2500 miles of cast iron pipe underground in 2005 What is the probability of at least two failures
Rearrange the polynomial:
a^2–2ab+b^2 - c^2
((a-b)(a-b))-c^2
(a-b)^2-c^2
Set x =a-b and y=c. The formula becomes
x^2-y^2
factoring this polynomial, we get
(x+y)(x-y)
Substituting back, we get:
(a+b+c)(a+b-c)
Let’s multiply it out to check:
A^2 -ab ac
- ab B^2 -bc
-ac bc -c^2
Answer:
$9000 at 4$
and
$10000 at 8%
Step-by-step explanation:
Let's assume that "x" is the amount deposited in the 4% account and "y" is the amount deposited in the 8% account.
Recall the formula for interest as : 
where I is the interest, R is the annual rate of interest and t is the number of years.
Since there are two investments, we need to add both interests at the end of the one year: I1 = x (0.04) (1) = 0.04 x and I2 = y (0.08) (1) = 0.08 y
Total Interest = Interest (from the 4% account) + Interest (from the 8% account)
Total Interest = $1160 = 0.04 x + 0.08 y
we also know that the total invested (x + y) adds to $19,000, that is:
$19,000 = x + y
Then we can solve these system of two equations by substitution, for example solving for y in the second equation and using the y substitution in the first equation;
y = 19000 - x
1160 = 0.04 x + 0.08 (19000 - x)
1160 = 0.04 x + 1520 - 0.08 x
0.08 x - 0.04 x = 1520 - 1160
0.04 x = 360
x = 360/0.04 = $9000
Then the other investment was : y = $19000 - $9000 = $10000