Which of the following equations demonstrate that the set of polynomials is not closed under the certain operations?
A. Subtraction: (3x^4+x^3)-(-2x^4+x^3)=5x^4
B. Addition: (x^2+x)+(x+1)=x^2+2x+1
C. Division: (x^2-5x+3)÷(x-2)=x-3+-3/x-2
D. Multiplication: (x^2-5x+3)(x-5)=x^3-10x^2+28x-15

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $32.09. find the probability that a randomly selected bill will have an amount greater than $155, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?

In the given triangle, ∠aed ∼ ∠ abc, ad = 6.9, ae = 7.2, de = 5.2, and bc = 10.2. find the measure of bd and ce. round your answer to the nearest tenth.

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297