1. Exponential growth follows the formula y=a(1+r)^x and exponential decay follows the formula y=a(1-r)^x..

This seems obviously TRUE

But now I'm having doubts about the decay formula

Is this true or false?

Normally exponential growth is expressed as

f(t) = a e^kt

and exponential decay is

f(t) = a e^-kt

If 0<r<1, then the statement is true, since then we have

1-r < 1 so we have a fraction, and exponential of a fraction is e^-kt for some k.

With no restrictions on r, things get a bit dicier.

I think in your case, say you have a 12% growth rate. Then

f(x) = a(1.12)^x

At 12% decay rate would then mean that 88% is left after each interval, so you would indeed have

f(x) = a(1-.12)^x = a(.88)^x

The statements regarding exponential growth and decay formulas are indeed true.

The formula for exponential growth is y = a(1+r)^x, where:
- "y" represents the final amount or value after a certain number of time periods.
- "a" is the initial amount or value at the starting point.
- "r" represents the growth rate, expressed as a decimal or fraction.
- "x" denotes the number of time periods that have passed.

On the other hand, the formula for exponential decay is y = a(1-r)^x, with similar variables:
- "y" still represents the final amount or value after a certain number of time periods.
- "a" remains the initial amount or value at the starting point.
- "r" represents the decay rate, expressed as a decimal or fraction (which is the opposite of the growth rate).
- "x" denotes the number of time periods that have passed.

So, in conclusion, both formulas are valid for exponential growth and decay, but they differ in the way the growth or decay rate is incorporated.