Can you find the error?

Both step 1 and step 2 were correct with the process of moving the value of x into the place of x and continuing to solve. However, step 3 is incorrect because when it is a negative value being subtracted by another negative value, it remains a negative. So the answer is -14 instead of 14.

, 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