does anyone know the formula used to find the *blank* term in an arithmetic series? Idk what formula to use!

Question

anonymous · Answer

PLEASE HELP!

anonymous · Answer

What is *blank term ??

anonymous · Answer

like when it says this: 
What is the 30th term of the arithmetic series 3, 7, 11, … ?
Thats my question. I just dont know what formula I need to use for that kind of thing

anonymous · Answer

And I have another question if you could help me with it I would really appreciate it!

anonymous · Answer

Oh so you can call it as nth term..

Formula for finding nth term is :
$$\large a_n = a + (n-1)d$$

Here: $a_n$ is nth term or we can say Last term also,
a is first term, n is total terms and d is common difference..

anonymous · Answer

What is the another one??

anonymous · Answer

What is the sum of the geometric sequence 1, –6, 36, … if there are 6 terms?

anonymous · Answer

thankyou so much for help with the other one!