Solve x2 + 4x – 12 = 0 by completing the square. Show your work for full credit.

Question

myininaya · Answer

first step add 12 on both sides
$$x^2+4x=12$$
now we want to complete the square on the left hand side so we need to add (b/2)^2
(4/2)^2=2^2=4
we add that on one side we have to do the same to other side
$$x^2+4x+4=12+4$$
$$(x+2)^2=16$$
take square root of both sides
$$x+2=\pm 4$$
now im pretty sure you can subtract 2 on both sides

anonymous · Answer

x^2 + 4x = 12
(x + 2)^2 -4  = 12
(x+2^2 =16
(x+2) = =4 or -4
x = x = 2 or -6