Answer:
2x^2 + 6x + 2
Step-by-step explanation:
5 + 3x - x^2 + (3x^2 - 5x + 4 + 8x - 7) =
= 5 + 3x - x^2 + 3x^2 + 3x - 3
= 2x^2 + 6x + 2
