Simplify the Expression: 9×9⁹ Power and Multiplication Problem

To solve this problem, let's apply the multiplication of powers rule:

• Step 1: Identify expression as $9 \times 9^9$.
• Step 2: Note that $9$ can be expressed as $9^1$.
• Step 3: Apply the exponent rule: $a^m \times a^n = a^{m+n}$.

Now, we'll work through the calculation step-by-step:

Step 1: Rewrite $9$ as $9^1$. Thus, our expression becomes $9^1 \times 9^9$.

Step 2: Use the exponent rule to combine: $9^1 \times 9^9 = 9^{1+9}$.

Step 3: Simplify the exponent by adding: $9^{1+9} = 9^{10}$.

Therefore, the simplified form of the expression is $9^{10}$.

In terms of the answer choices, the correct answer is

$9^{1+9}$