A person invests 7000 dollars in a bank. The bank pays 6.25% interest compounded annually. To the nearest tenth of a year, how long must the person leave the money in the bank until it reaches 19900 dollars?

answer: 2x + 2 − 2 = 10 − 2; subtraction property of equality

step-by-step explanation:

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for