Answer :

To simplify the expression

[tex]$$x^9 \cdot x,$$[/tex]

we use the property of exponents which states that when multiplying powers with the same base, we add the exponents. In general, for any nonzero number [tex]$x$[/tex] and exponents [tex]$a$[/tex] and [tex]$b$[/tex], we have

[tex]$$x^a \cdot x^b = x^{a+b}.$$[/tex]

Here, the two exponents are [tex]$9$[/tex] (from [tex]$x^9$[/tex]) and [tex]$1$[/tex] (since [tex]$x = x^1$[/tex]). Adding these gives

[tex]$$9 + 1 = 10.$$[/tex]

Thus, the simplified expression is

[tex]$$x^{10}.$$[/tex]

So, the final answer is:

[tex]$$\boxed{x^{10}}.$$[/tex]