Question

obtenha os zeros
a)
$f(x) = x {}^{2} - 7x + 12$
b)
$y = - 3x {}^{2} + 9x$
pro favor e para agora​

Answer 1

a) x² - 7x + 12 = 0

a = 1

b = - 7

c = 12

∆ = b² - 4 . a . c

∆ = (-7)² - 4 . 1 . 12

∆ = 49 - 48

∆ = 1

x = - b ± √∆

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

2a

x' = - (-7) + 1

-----------

2 . 1

x' = 7 + 1

--------

2

x' = 8

---

2

x' = 4

x" = - (-7) - 1

-----------

2 . 1

x" = 7 - 1

------

2

x" = 6

---

2

x" = 3

S = { 4 , 3}

b) -3x² + 9x = 0

a = - 3

b = 9

c = 0

∆ = b² - 4 . a . c

∆ = 9² - 4 . (-3) . 0

∆ = 81 + 0

∆ = 81

x = - b ± √∆

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

2a

x' = - 9 - 9

---------

2 . (-3)

x' = - 18

------

- 6

x' = 3

x" = - 9 + 9

----------

2 . (-3)

x" = 0

----

- 6

x" = 0

S = {0 , 3}