Solve (25a+4b)/(7y+14) = 9b: Identifying the Application Domain

To solve the problem, follow these steps:

• Step 1: Understand that the equation $\frac{25a+4b}{7y + 4 \cdot 3 + 2}=9b$ is undefined when the denominator equals zero.
• Step 2: Simplify the denominator: $7y + 4 \cdot 3 + 2$.
• Step 3: Calculate the constant part: $4 \cdot 3 = 12$, so the expression becomes $7y + 12 + 2$.
• Step 4: Combine constants: $12 + 2 = 14$. The denominator is $7y + 14$.
• Step 5: Set the denominator equal to zero to find values of $y$ that make the equation undefined: $7y + 14 = 0$.
• Step 6: Solve for $y$:
• Subtract 14 from both sides: $7y = -14$.
• Divide by 7: $y = -2$.

Therefore, the equation is undefined when $y = -2$. The field of application excludes $y = -2$.

The choice that reflects this is $\boxed{y \neq -2}$.