The density of a certain cell in blood peaks at 1900 cells/L

[nope187]

The density of a certain cell in blood peaks at 1900 cells/L and lows at 0. Fluctuations occur over a 21 day period. Model an equation for this trend d(t) = density wrt time. Model the temporal dynamics of the cells in days assuming that the density is at highest during day 0.

Ive tried to model the equation by saying its d(t) = 1900-(1900/21)t but it isn't correct.
can anyone please help me?
thanks in advance

 

[stapel]

The density of a certain cell in blood peaks at 1900 cells/L and lows at 0. Fluctuations occur over a 21 day period....

You are given that the measured values periodically vary between a fixed low and a fixed high. Perhaps a periodic function (like a cosine, maybe) would be helpful here...?

 

[nope187]

thanks m8