x^(n+1). When we are multiplying variables with exponents, the rule is that we add the exponents together — for example, if I were to multiply 2^2 and 2^4, I’d get 2^6 (which is 2+4). This works the same:
If we consider that any number is actually itself to the first power so (x is the same as x^1) then if we multiply x^1 * x^n we get x^(n+1).