The simplified form of the given expression is:

$12 - 13y^2$

Would you like more details on the steps?

Here are 5 related questions for further practice:

1. How would the expression change if the coefficient of $y^2$ were doubled?
2. What is the result if you substitute $y = 2$ into the simplified expression?
3. How do you factor $12 - 13y^2$?
4. What happens if you add a linear term $-7y$ to the simplified expression?
5. Can you solve the equation $12 - 13y^2 = 0$?

Tip: Always check your expressions for common factors before simplifying; this might make the simplification process easier!