Question

A) 3x2 - 6x - 72=0.. (Obs: O 2 é em cima do "x")

Answer 1

${3x}^{2} - 6x - 72 = 0 \\ a = 3 \\ b = - 6 \\ c = - 72 \\ delta = {b}^{2} - 4ac \\ { - 6}^{2} - 4 \times 3 \times ( - 72) \\ 36 + 864 = 900 \\ \sqrt{900} = 30 \\ \\ x1 = \frac{ - b + \sqrt{900} }{2a} \\ x1 = \frac{6 + 30}{6} \\ x1 = \frac{36}{6} \\ x1 =6 \\ \\ x2 = \frac{ -b - \sqrt{900} }{2a} \\ x2 = \frac{6 - 30}{6} \\ x2 = \frac{ - 24}{6} \\ x2 = - 4$