simplify 3x^2+6-2x+5x-4x^2+9

-rearrange to group like terms:

3x^2 - 4x^2 + 5x - 2x + 6 + 9

-combine like terms:

-x^2 + 3x + 15

Therefore, the simplified expression is -x^2 + 3x + 15.

simplify 4x^2+8x-11x+6-5x^2+2

-rearrange to group like terms:

4x^2 - 5x^2 + 8x - 11x + 6 + 2

-combine like terms:

-x^2 - 3x + 8

Therefore, the simplified expression is -x^2 - 3x + 8.

To simplify the expression 3x^2 + 6 - 2x + 5x - 4x^2 + 9, you can combine like terms:

First, combine the terms with the same variable and degree:
(3x^2 - 4x^2) + (-2x + 5x) + 6 + 9

Simplify the coefficients of the like terms:
(-x^2) + (3x) + 6 + 9

Combine the constant terms:
(-x^2) + (3x) + 15

Therefore, the simplified form of the expression 3x^2 + 6 - 2x + 5x - 4x^2 + 9 is -x^2 + 3x + 15.