Réponse:
A= (2x - 5) (-x + 5)
A= 2x×(-x) + 2x×5 + 5×x - 5×5
A= -2x² + 10x + 5x - 10
A= -2x + 15x - 10
B= (-5x + 2) (7x - 5)
B= -5x×7x + 5x×5 + 2×7x - 2×5
B= -35x² + 25x + 14x - 10
B= -35x² + 39x - 10
C= (8/4 + x) (1/4x - 2)
C= 8/4×1/4x - 8/4×2 + x×1/4x - x×2
C= 2/4x - 8/2 + 1/4x² - 2x
C= 2/4x - 2x - 8/2 + 1/4x²
C= -6/4x - 8/2 + 1/4x²