Question

seja f:r-r definida por f(x)= (2x+1).(x-3). determine os elementos do dominio cuja image, e -5

Answer 1

f(x) = -5

$f(x) = (2x + 1) \times (x - 3) \\ - 5 = 2 {x}^{2} - 6x + 1x - 3 \\ 0 = 2 {x}^{2} - 5x - 3 + 5 \\ 0 = 2 {x}^{2} - 5x + 2$

// Bhaskara

∆ = b² - 4ac
∆ = (-5)² - 4 . 2 . 2
∆ = 25 - 16
∆ = 9

x = (-b ± √∆)/2a
x = [-(-5)±√9)/2 . 2
x = (5 ± 3)/4

x' = (5 + 3)/4
x' = 8/4
x' = 2

x'' = (5 - 3)/4
x'' = 2/4
x'' = 1/2

S = {1/2, 2}