(5x² + 6x – 3) – (2x² – 3x – 4) = 5x² + 6x – 3 – 2x² + 3x + 4 = (5x² – 2x²) + (6x + 3x) + (– 3 + 4) = 3x² + 9x + 1
Ответ: 3x² + 9x + 1