Question

Quais os zeros da f(x) = x² ‒ 4x ‒ 5 * 2 pontos A) S = {‒ 1, 5} B) S = {‒2, 7} C) S = {4, 2} D) S = { 7, 3}

Answer 1

x² - 4x - 5 = 0

∆ = b² - 4 . a . c

∆ = (-4)² - 4 . 1 . (-5)

∆ = 16 + 20

∆ = 36

x = - b ± √∆

-------------

2a

x' = - (-4) - 6

------------

2 . 1

x' = 4 - 6

-------

2

x' = - 2

---

2

x' = - 1

x" = - (-4) + 6

------------

2 . 1

x" = 4 + 6

-------

2

x" = 10

---

2

x" = 5

S = {-1 , 5}

Letra A