Solve by completing the square. x^2 + 4x - 1 = 0

x = - 2 ± sqrt (5)

Step-by-step explanation:

x^2 + 4x - 1 = 0

Add 1 to each side

x^2 + 4x - 1+1 = 0+1

x^2 + 4x = 1

Take the coefficient of x

4

Divide by 2

4/2 = 2

Square it

2^2=4

Add it to each side

x^2 + 4x+4=1+4

(x+2) ^2 = 5

Take the square root of each side

sqrt ((x+2) ^2) = ± sqrt (5)

x+2 = ± sqrt (5)

Subtract 2 from each side

x+2-2 = - 2 ± sqrt (5)

x = - 2 ± sqrt (5)