Let's simplify the given expression:

$(-10x^2 + 4x) - (-4x^2 + 6x + 8)$

Step 1: Distribute the negative sign across the second parentheses

$= -10x^2 + 4x + 4x^2 - 6x - 8$

Step 2: Combine like terms

$(-10x^2 + 4x^2) + (4x - 6x) - 8$

$= -6x^2 - 2x - 8$

So, the simplified expression is:

$-6x^2 - 2x - 8$

Would you like further details on any step?

Here are 5 related questions:

1. How do you factor quadratic expressions like $-6x^2 - 2x - 8$?
2. What is the importance of distributing negative signs in expressions?
3. How can you graph a quadratic expression like $-6x^2 - 2x - 8$?
4. How do you solve a quadratic equation when it is set to 0?
5. What are common mistakes when combining like terms?

Tip: Always be cautious with negative signs when distributing them across terms in parentheses.