Question

Quais são as raizes da equação x2-3×-4=0

Answer 1

$x^2 - 3x - 4 = 0 \\ a = 1, b = -3, c = -4 \\ \\ \Delta = b^2 - 4ac \\ \Delta = (-3)^2 - 4 \times 1 \times -4 \\ \Delta = 9 + 16 \\ \Delta = 25 \\ \\ x = \frac{-b \pm \sqrt{\Delta} }{2a} \\ x = \frac{-(-3) \pm \sqrt{25} }{2 \times 1} \\ x = \frac{3 \pm 5}{2} \\ \\ x_1 = \frac{3 + 5}{2} = \frac{8}{2} = 4 \\ \\ x_2 = \frac{3 - 5}{2} = \frac{-2}{2} = -1 \\ \\ x = 4, -1$

Answer 2

x² - 3x - 4 = 0
a = 1; b = - 3; c = - 4
Δ = b² - 4ac
Δ = (-3)² - 4.1.(-4)
Δ = 9 + 16
Δ = 25

x = - b +/- √Δ   =  - (-3) +/- √25
      --------------     -------------------
              2a                 2.1

x = 3 + 5
      --------  = 8/2 = 4
          2

x = 3 - 5
      --------  = - 2/2 = - 1
          2

R.: x = 4 e x = - 1