various basic algebra problem in MTH 133 unit 3--B

For noninteger answers, I have to write my answers as a fraction rather than a decimal.

To show my work, I need to include
o the algebra used to compute the solution to any equations.
o the formula with substituted values.
o the final calculated answer with units.
Please see attachment.

1) Solve the following algebraically. You must show all your work.
2) Solve algebraically and check your potential solutions: sqrt(x +20) -x = 0
3) a) Show the steps that you would take to solve the following algebraically:
b) What potential solution did you obtain? Explain why this is this not a solution.
4) For the following function, C computes the cost in millions of dollars of implementing a city recycling project when x percent of the citizens participate.
a) Using this model, approximately what is the cost if 60% of the citizens participate?
b) Using this model, estimate the percentage of participation that can be excepted if $4 million is spent on this recycling project. Set up an equation and solve algebraically. Round to the nearest whole percent.
5) The volume of a cube is given by V = s3, where s is the length of a side. Find the length of a side of a cube if the volume is 500 cm3. Round answer to three decimal places.
6) Suppose that N= sqrt(x) + 3 models the number of cases of an infection, in millions, of a disease x years from now.
a) Approximately how many cases of the infection will there be 9 years from now?
b) In approximately how many years will there be 5 million cases?
7) a) If y = sqrt(x) - 2, fill in the following table for x = 0,1,2,3,4. Round to three decimal places where necessary.
b) Explain why no negative values are chosen as values to substitute in for x.
c) Graph in MS Excel and paste your graph here.