a recreational swimming lake is treated to control bacteria. suppose t days after a treatment the concentration of bacteria per cubic centimeter is given by c(t)=30t^2-240t+500; 0

Question

a recreational swimming lake is treated to control bacteria. suppose t days after a treatment the concentration of bacteria per cubic centimeter is given by c(t)=30t^2-240t+500; 0<t<8. how many days after treatment will the concentration of bacteria be minimal? what is the minimum concentration?

anonymous · Answer

differentiate  
60t - 240 = 0 for minmm
t = 6 days

minm concentrtation is
30(36) - 240*6 + 500
= 1080 -  1440 + 500
= 140

anonymous · Answer

oh  sorryyyyy - i cant count!  t = 4 days!
minm concentration 
=  30*16 - 240*4 + 500

anonymous · Answer

do u follow that ok ?

anonymous · Answer

my brain did a 'switch off'  for a moment

anonymous · Answer

yeah i think! so the minimum concentration would be 20?

anonymous · Answer

480 -960 + 500 = 20
right

anonymous · Answer

awesome thanks so much!!!

anonymous · Answer

no probs