a) h² = AH² = AB² - BH² = 9² - (BM+MH)² = 81 - (x+3)² = 81 - x² - 6x - 9 = -x² - 6x + 72
de meme AH² = AC² - HC² = 6² - (MC-MH)² = 36 - (x-3)² = 36 - x² + 6x - 9 = -x² + 6x + 27
b) -x² + 6x + 27 = -x² - 6x + 72
12x = 72 - 27 = 45
x = 15/4