Answer:
The equation for the nth term of the given arithmetic sequence is: 
Step-by-step explanation:
We need to write an equation for the nth term of the arithmetic sequence:
15,28,41 ....
The equation for arithmetic sequence is: 
Where
is the nth term,
is first term and d is common difference
In the given sequence we have:
a₁ = 15
a₂ = 28
We can find common difference using the formula:

So, the common difference d is 13
Now, equation for nth term will be:

So, the equation for the nth term of the given arithmetic sequence is: 
where n=1,2,3..