SOLUTION: The concentration, in parts per million, of a particular drug in a patient's blood x hours after the drug is administered is given by the function f(x)=-x^4+13x^3-47x^2+99x How

Algebra ->  Functions -> SOLUTION: The concentration, in parts per million, of a particular drug in a patient's blood x hours after the drug is administered is given by the function f(x)=-x^4+13x^3-47x^2+99x How      Log On


   

Question 148454: The concentration, in parts per million, of a particular drug in a patient's blood x hours after the drug is administered is given by the function
f(x)=-x^4+13x^3-47x^2+99x
How many hours after the drug is adminstered will it be eliminated from the bloodscream?
I used x=-b/2a and came up with 6. The answer was incorrect.
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
x=-b/2a is for the axis of symmetry of a parabola __ highest order term is squared

factoring __ f(x)=(x)(-x^3+13x^2-47x+99)

factors of 99 __ ±1, ±3, ±9, ±11, ±33, ±99 __ testing the factors shows 9 as a solution