6n-5 is the nth term of this sequence
3n - 7
It is Un = 3n - 7.
The nth term is: 3n+2 and so the next number will be 20
Un = 4n - 13.
It is not possible to answer the question since a non linear sequence could be geometric, exponential, trigonometric etc.
You need the rule that generates the sequence.
If the sequence is non-linear, you need to establish how it is defined.
It is the sequence of first differences. If these are all the same (but not 0), then the original sequence is a linear arithmetic sequence. That is, a sequence whose nth term is of the form t(n) = an + b
It is the description of a rule which describes how the terms of a sequence are defined in terms of their position in the sequence.
Un = n + 32
Increase each term by 1.05 and so the next term is 6+1.05 = 7.05
It is a sequence of numbers which is called an arithmetic, or linear, sequence.
"Non-linear sequence" is a generic term for just about ANY sequence, each of which will have a different equation.
You first have to figure out some rule for the sequence. This can be quite tricky.
There are infinitely many possible answers. The simplest, linear, rule is Un = 4n - 17 for n = 1, 2, 3, ...
It appears that a number of -79 is missing in the sequence and so if you meant -58 -65 -72 -79 -86 then the nth term is -7n-51 which makes 6th term in the sequence -93
Any iterative sequence.