Need help in derivatives! (Urgent)

1. Oct 18, 2005

envanyatar

I need help in the following question:
"The rate of increase of the rate of Inflation is decreasing" Write this sentence in terms of derivatives of average prices.

t= time
therefore, Rate of change of price = dp/dt = Inflation = I

therefore, rate of increase of the rate of Inflation = I'

therefore, I' = (d^2p)/(dt^2)

Since the rate of increase of the rate of Inflation is decreasing;

I' = - (d^2p)/(dt^2)

I just like to ask whether this is correct.
Thanks.

2. Oct 18, 2005

whozum

When a function f(x) is decreasing, $\frac{df}{dx}$ is always negative..