Here is your equation:
[tex] a^{4} \times a [/tex]
First simplify the exponent.
[tex] a^{4} = a \times a \times a \times a [/tex]
Since the power is 4, you multiply a 4 times. Don't forget about the remaining a. Add that and it becomes:
[tex] a \times a \times a \times a \times a [/tex]
It is the same as [tex] a^{5} [/tex] because you're multiplying 5 a's. That's why the power is 5.
Your answer is [tex] a^{5} [/tex]