Question

x2-x-1=0 solve by the formula method​

Answer 1

Answer:

$x_{1}$ = 1 + $\sqrt{5}$ / 2

$x_{2}$ = 1 -$\sqrt{5}$ / 2

Step-by-step explanation:

$x^2$ - x - 1 = 0

a = 1 , b = -1 , c = -1

D = $b^2$ - $4ac$

  = $(-1)^2$ - 4(1)(-1)

  = 1 + 4

  = 5

$\sqrt{D}$  = $\sqrt{5}$

$x_{1}$ = -b + $\sqrt{D}$ / 2a

    = 1 + $\sqrt{5}$ / 2

$x_{2}$ = -b - $\sqrt{D}$ / 2a

   = 1 -$\sqrt{5}$ / 2