Element X is a radioactive isotope such that every 20 years, its mass decreases by half. Given that the initial mass of a sample of Element X is 410
grams, how long would it be until the mass of the sample reached 270 grams,
to the nearest tenth of a year?

p

Step-by-step explanation:

cause i said so

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb

justin bieber ml.