To find the numerical equivalent of the expression \( 12^{-5} \cdot 12^7 \), we will use the product rule of integer exponents. The product rule states that when multiplying two expressions with the same base, you can add their exponents. In mathematical terms:
\[
a^m \cdot a^n = a^{m+n}
\]
Step-by-Step Calculation:
Step 1: Identify the base and exponents
- Here, the base is \( 12 \).
- The exponents are \( -5 \) and \( 7 \).
Step 2: Apply the product rule
Using the product rule:
\[
12^{-5} \cdot 12^7 = 12^{-5 + 7}
\]
Step 3: Simplify the exponent
Now we calculate the exponent:
\[
-5 + 7 = 2
\]
So:
\[
12^{-5} \cdot 12^7 = 12^{2}
\]
Step 4: Calculate \( 12^2 \)
Now we compute \( 12^2 \):
\[
12^2 = 12 \times 12 = 144
\]
Conclusion
The numerical equivalent of \( 12^{-5} \cdot 12^7 \) is:
\[
\boxed{144}
\]
Explanation of the Product Rule
In this calculation, we applied the product rule of integer exponents effectively by recognizing that both terms share the same base \( 12 \). By adding their exponents, we simplified the multiplication of the two terms into a single term with an easily computed exponent.
Using this method allowed us to convert a more complex expression into a simpler form, facilitating the calculation of the final result efficiently.