Step-by-step explanation:
3(x + 1)(x + 7) − (2x + 5)²
3(x² + 8x + 7) − (4x² + 20x + 25)
3x² + 24x + 21 − 4x² − 20x − 25
-x² + 4x − 4
-(x² − 4x + 4)
-(x − 2)²
A squared number is never negative (provided x is a real number), so -(x − 2)² is never positive.
