Answer:
Use the formula for Arithmetic only if it is Arithmetic: a1+ (n-1)d
a represents the first number in the sequence, n represents the number, and d represent common difference
Use the formula for geometric sequence: an=a1r the exponent of r to n-1
an represents the nth term you are trying to find, a1 represents the first number, r represents the common ratio, and n-1 is just the nth term minus 1.
Once you figure out if the sequence is arithmetic or geometric you one of those formulas.