Math Again.?

1. A scientist is doing an experiment with a chemical that has a half- life of 11 days. How much of the chemical will be remaining after 40 days if there were 300 grams at the begining of his lab?

2. y= 2/3x^3 -2x^2 -30x
For what values in the domain is the above function increasing?
For what values in the domain is the above function decreasing?

3. A real estate office handles 50 apartment units. when the rent is $270 permonth all units are occupied. However, on the average, for each $15 increase in rent , one unit becomes vacant. also, each occupied unit requires an average of $18 per month for service and repairs. Write an equation that describes the profit in the given situation .

every 11 days the substance halves its mass
day1 300g
day11 150g
day22 75g
day 33 37.5
day 44 18.75g

2. y= 2/3x^3 -2x^2 -30x
2/x( 3x^2 -x -30)
2/(3x - 10)(x+ 3)


usign the zero property 3x-10=0 or x+3=0
x = +10/3 or x = -3
those are the vertical asymptotes
now it is yr job to plug in values of x on either side of these to see increasign or decreasing