Bonjour
A = 5x (x - 3) - 7 (2x - 5)
A = 5x² - 15x - 14x + 35
A = 5x² - 29x + 35
B= (4x - 1)²
B = 16x² - 8x + 1
C = (3x + 5)² - (4 - 3x)(4 + 3x)
C = 9x² + 30x + 25 - (16 - 9x²)
C = 9x² + 30x + 25 - 16 + 9x²
C = 9x² + 9x² + 30x + 25 - 16
C = 18x² + 30x + 9