contestada

Using the completing the square method, which of the following is the solution to x2 + 4x - 7 = 0?


A.x = -2 - √11, x = -2 + √11


B.x = 2 - √3, x = 2 + √3


C.x = 2 - √11, x = 2 + √11


D.x = -2 - √3, x = -2 + √3

Respuesta :

kudzordzifrancis
We are completing the square for

[tex]x^2+4x-7=0[/tex]

Add +7 to both sides
[tex]x^2+4x=7[/tex]

Next add

[tex](\frac{4}{3})^2[/tex]
to both side

Notice that the Left hand side is a perfect square. That is

[tex](x+2)^2= 7+4[/tex]

[tex](x+2)^2= 11[/tex]
Take square root of both sides

[tex](x+2)= \mp \sqrt(11)[/tex]
[tex]x= -2 \mp \sqrt(11)[/tex]

[tex]x= -2 - \sqrt(11)\: or \:x= -2 - \sqrt(11)[/tex]
[tex] <B>The correct answer is A</B>[/tex]

Otras preguntas