Answer:

Step-by-step explanation:
- Cross multiply.
- Add like terms.
- Simplify.
Option C:
The coefficient of
is 40.
Solution:
Given expression:

Using binomial theorem:

Here 
Substitute in the binomial formula, we get

Now to expand the summation, substitute i = 0, 1, 2, 3, 4 and 5.


Let us solve the term one by one.






Substitute these into the above expansion.

The coefficient of
is 40.
Option C is the correct answer.
Answer:
B. 95% confident the average concentration of PCBs in the water supply is between 2.9 ppb and 3.5 ppb
Step-by-step explanation:
You are given the total number of samples, the concentration of lead, and the standard deviation. The standard deviation represents how inaccurate the estimation of the concentration of lead in the drinking water. This means that there can only possibly be a 0.3 ppb error in the estimation. 3.2-0.3=2.9, and 3.2+0.3=3.5

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