Resposta :
A = x-3 ====> A² = (x-3)² ===> A² = x² - 6x + 9
B = x² + 3
C = 9x
A² - B + C = (x² - 6x + 9) - (x² + 3) + 9x
x² - 6x + 9 - x² - 3 + 9x =
3x + 6 = 3(x+2)
B = x² + 3
C = 9x
A² - B + C = (x² - 6x + 9) - (x² + 3) + 9x
x² - 6x + 9 - x² - 3 + 9x =
3x + 6 = 3(x+2)