Algebra Problem

[annie28]

The concentration C of a medication in the blood stream t hours after being administered is given by C(t)= -0.002t^4+0.039t^3-0.285t^2+0.766t+0.055.

A) After how many hours will the concentration be the highest?
B) A woman nursing a child must wait until the concentration is below 0.5 before she can feed him. After taking the medications, how long must she wait before feeding?

I have entered this into my graghing calculator a dozen times, but my calculator just tells me that there is an error after I enter the problem.. Could someone help me figure out how to enter in into my TI-83 calculator?

Thank You,
Annie

 

[galactus]

Did you enter 't' in as the variable in your calculator?. If so, that's the problem. It only accepts 'x' as the variable.

Also, make sure nothing is stored in 'x'.

I assume you have not taken calculus?. If not, then the easiest way may be to just graph the expression and see where the high points are.

Remember, use x instead of t. For the part b:

\(\displaystyle -0.002t^{4}+0.039t^{3}-0.285t^{2}+0.766t+0.055<0.5\).