To simplify the expression $8y^2 - 2y + 5 - 6y^2 - 2y + 4$, combine like terms:

1. Combine $y^2$ terms: $8y^2 - 6y^2 = 2y^2$
2. Combine $y$ terms: $-2y - 2y = -4y$
3. Combine constant terms: $5 + 4 = 9$

Putting it all together, the simplified expression is:

$2y^2 - 4y + 9$

Would you like more details or have any questions? Here are some related questions you might find interesting:

1. How do you factor a quadratic expression?
2. What are the roots of the quadratic equation?
3. How does this expression change if $y$ is a specific value?
4. Can you explain the significance of the coefficients in a quadratic?
5. How would you graph this quadratic function?

Tip: Always combine like terms first when simplifying expressions!