Suppose Alex has 3x stamps, Freddy has 5x stamps. After Freddy gives Alex 10 stamps, Alex has 3x+10 while Freddy has 5x-10
the new ratio is 7 to 9, so we have the equation: (3x+10)/(5x-10)=7/9
9(3x+10)=7(5x-10)
27x+90=35x-70
160=8x
x=20
So Alex has 3*20=60 stamps while Freddy has 5*20=100. Together they have 160
2. f(x) = x - 2x² - 5 + 10x
=-2x² + 8x - 5
f'(x)= -4x + 8
4. y = 100(45x - 30 - 3x³ + 2x²)
= 100(-3x³ + 2x² + 45x -30)
= -300x³ + 200x² + 4500x - 3000
y' = -900x² + 400x + 4500
First, you factor and simplify (respectively) the numerator and denominator. Your equation becomes:

Notice, there is a (x + 7) on both the top and the bottom. Because of this, they cancel each other out. What is left is your answer:
Answer:
option 1 not function....
A) 0.9803; 0.4803
B) 32
We calculate the z-score for this problem by using the formula:

Using our formula, we have:

Using a z-table (http://www.z-table.com) we see that the area to the left of, less than, this score is 0.9803.
To find the probability it is between the mean and this, we subtract the probability associated with the mean (0.5) from this:
0.9803 - 0.5 = 0.4803.
To find B, we first find the z-score for this. Using a z-table (http://www.z-table.com) we see that the closest z-score would be 2.33. We then set up our equation as

Multiplying both sides by 0.85 we have
2.33(0.85) = 0.35√n
1.9805 = 0.35√n
Divide both sides by 0.35:
1.9805/0.35 = √n
Square both sides:
(1.9805/0.35)² = n
32 ≈ n