Question

In 1999, a sample of a radioactive substance had a mass of 750 milligrams. Since then, the sample has decayed by 7.1% each year.

Let t be the number of years since 1999. Let y be the mass of the substance in milligrams,
Write an exponential function showing the relationship between y and t.

Answer 1

Below

Explanation:

If it decays 7.1 % ( which is .071 in decimal ) then .929 remains at the end of each year and the equation becomes

y = 750 (.929^t) where t is years since 1999 and y is mg