Verified answer

(3x + 2)² - 3*(x - 4)² -x*(x + 16) + (x - 3)²

9x² + 12x + 4 - 3*(x² - 8x + 16) - x² - 16x + x² - 6x + 9

9x² - 3x² - x² + x² + 12x + 24x - 16x - 6x + 4 - 48 + 9

6x² + 14x - 35 = 0

delta

d² = 14² + 24*35 = 1036 = 4*259

d = 2*√259

x1 = (-14 + 2*√259)/12 = (-7 + √259)/6

x2 = (-14 - 2*√259)/12 = (-7 - √259)/6

pronto