The radioactive substance strontium-90 has a half-life of 28 years. in other words, it takes 28 years for half of a given quantity of strontium-90 to decay to a non-radioactive substance. the amount of radioactive strontium-90 still present after t years is modeled by the expression 80*2^t/28 grams. evaluate the expression for t = 0, t = 28 and t = 56. what does each value of the expression represent?

19.

step-by-step explanation:

you add the 9 in the tens column since it is a single digit and 9 plus zero is 9 so it is 19

see explanation

step-by-step explanation:

since the sequence is geometric there is a common ratio r between consecutive terms, that is

r = 4 ÷ - 2 = - 2

r = - 8 ÷ 4 = - 2

r = 16 ÷ 8 = - 2

the next term - 13 must be incorrect as it should be - 32 for the sequence to be geometric.

the first 4 terms are therefore geometric with common ratio r = - 2