Solve x2 + 4x – 4 = 8 for x.

A. –6 or x = 2
B. x= -2 + or - 2 with a square root of 2
C. x = –2 or x = 6
D. x= 2 + or - 2 with a square root of 2

Respuesta :

A. x=-6 or x=2
Quadratic equation

we know that

To find the solution let's factor the equation

[tex] x^{2} + 4x - 4 = 8 [/tex]

Group terms that contain the same variable, and move the constant to the opposite side of the equation

[tex] x^{2} + 4x = 8+4 [/tex]

[tex] x^{2} + 4x = 12 [/tex]

Complete the square. Remember to balance the equation by adding the same constants to each side

[tex] x^{2} + 4x+4 = 12+4 [/tex]

[tex] x^{2} + 4x+4 = 16 [/tex]

Rewrite as perfect squares

[tex] (x+2)^{2} = 16 [/tex]

[tex] (x+2)^{2} = 16\\ (x+2)=(+/-)\sqrt{16} \\ x1=-2+\sqrt{16} =-2+4=2\\ x2=-2-\sqrt{16} =-2-4=-6 [/tex]

therefore

the answer is the option

A. –6 or x = 2