Question

Dada a função f(x)=2x²+6x-8 indentifique a raiz

Answer 1

2x²+6x-8 /2
X² + 3X - 4

B²-4AC
3²-4*1*-4
9+16
25

-3+-5 / 2

-3+5/2 = 2/2 = 1
-3-5/2 = -8/2=-4

Answer 2

f(x) = 2x² + 6x - 8
0 = 2x² + 6x - 8
2x² + 6x - 8 = 0 (:2)
x² + 3x - 4 = 0

a = 1; b = 3; c = - 4

Δ = b² - 4ac
Δ = 3² - 4.1.(-4)
Δ = 9 + 16
Δ = 25

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

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

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

R.: x = 1 e x = - 4