(4x2–10)+(–10x2–6x+3).

Sure, let's solve this step by step:

1. First, let's simplify the expression within each parenthesis:

   (4x^2 - 10) simplifies to 4x^2 - 10.

   (-10x^2 - 6x + 3) simplifies to -10x^2 - 6x + 3.

2. Now, let's add these two simplified expressions together:

   (4x^2 - 10) + (-10x^2 - 6x + 3) = 4x^2 - 10x^2 - 6x - 10 + 3.

3. Finally, let's combine like terms:

   4x^2 - 10x^2 - 6x - 10 + 3 = -6x^2 - 6x - 7.

So, the simplified form of the given expression is -6x^2 - 6x - 7.