How could you explain the operation symbols for addition (+) and multiplication (x).

Refer below for the explanation.

Step-by-step explanation:

Addition (+) symbol tells that you have to join the numbers in order to make a sinhle number for ex,

2+2=4.

Whereas multiply(×) refers that you have to add those number how many times for ex,

2×2=4.

So 2 have been join 2 times. So that becomes 4.

, 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