correct ... C(4) = 20 bacteria/cm^3A swimming pool is treated periodically to control the growth of bacteria. Suppoe that t days after a treatment, the concentration of bacteria per cubic cm is C(t)=30t^9-240t+500. Find the lowest concentration of bacteria during the first week after the treatment.
C(t) = 30t^2 - 240t + 500 instead of 30t^9 ... ?
Ok.. what I did.. I think i did right, but the back of the book.. just wondering if they are wrong. Just making sure, please confirm with me.
My work is below:
c'(t)=0 when 60t-240=0
f(4)=0 C(4) = 20
f(0)=-240 C(0) = 500
f(7)=180 C(7) = 290
therefore the lowest concentration of bacteria during the first week after the treatment is 0 cm^3 on the 4th day
That is my answer. However, the back of the book says.. 20