Let's simplify the expression:

$(-10x^2 + 4) + (-9x - 6)$

Step-by-step:

1. Combine like terms.
   • There is no other $x^2$ term, so $-10x^2$ remains as it is.
   • There is no constant that combines with $-9x$, so $-9x$ remains as it is.
   • Combine the constants: $4 + (-6) = -2$.

So, the simplified expression is:

$-10x^2 - 9x - 2$

Would you like more details or have any questions?

Here are 5 related questions to explore:

1. How do you solve quadratic equations like $-10x^2 - 9x - 2 = 0$?
2. How do you factor quadratic expressions?
3. What is the quadratic formula and how is it used?
4. How do you add and subtract polynomials?
5. How do you graph a quadratic equation?

Tip: When simplifying expressions, always group like terms (terms with the same variable raised to the same power).