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- September 30th 2008, 07:17 PM #1

- Joined
- Aug 2008
- Posts
- 32

## pre cal help

1. what is the area of a square whose diagnol is 1 unit longer than the length of a side?

2. if a 3 didget number is chosen at random, from the set of all 3 diget numbers what is the probablility all 3 didgets will be prime?

3. x+y=b

x+2y=b^2

for what value of "b" will the solution of the system consist of pairs of positive numbers?

4. Find the equation of a line perpendicular to 3x-5y=17 that goes throgh the point (4,3)

5.ms sanders has Epogen 2200 units subcutaneous injection 3 times a week ordered for the anemia caused by chronic renal failur. Epogen 3000units/ml is avalible. How many millilieters will the patient recieve for each dose?

- September 30th 2008, 10:16 PM #2

- September 30th 2008, 10:33 PM #3
3. Use the elimination method to get in terms of . Substitute back into equation 1 to get in terms of .

You should get and .

You want both x and y to be positive.

So and .

Solving the first gives...

and so, dividing by b, we get

if and if .

Solving the second gives...

and so if and if .

So putting the inequalities together, we find that if , b is both greater than 1 and greater than 2. So . And if we find that b is both less than 1 and less than 2. So .

- September 30th 2008, 11:10 PM #4

- Joined
- Jun 2008
- Posts
- 792

Another way to solve number 1:

Knowing that in a 45-45-90 triangle the hypotenuse is \sqrt(2) multiplied by side:

EDIT:

As for number 4, simply solve for y to get the function in the form of:

Recall that m is the slope, and that the slope of a line that is perpendicular to the line in question is given by:

Once you have the slope and the given point, simply plug in point slope form:

and solve for y.