To solve the equation \( (y^{-9})^b = y^{45} \), we can use the property of exponents which states that \( (a^m)^n = a^{m \cdot n} \).
Applying this to our equation, we have:
\[ (y^{-9})^b = y^{-9b} \]
Now we can rewrite the equation:
\[ y^{-9b} = y^{45} \]
Since the bases (y) are the same, we can set the exponents equal to each other:
\[ -9b = 45 \]
Next, we solve for \( b \):
- Divide both sides by -9:
\[ b = \frac{45}{-9} = -5 \]
Thus, the value of \( b \) is \( -5 \).
So the answer is:
–5