X² – 4x – 12=0
solve by completing the square

x = -2 0r x = 6

Step-by-step explanation:

from the question

X² – 4x – 12=0

solve by completing the square method

we have;

X² – 4x – 12=0

X² – 4x = 12

to make the left hand side a perfect square we add 4 to both sides.

X² -4x  + 4 = 12 + 4

X² -4x  + 4 = 16

from left hand side X² -4x  + 4

= (x -2) × ( x -2)

it can be simply expressed as

( x-2)²

so since X² -4x  + 4  has been simplified to be ( x-2)²

then,

( x-2)² = 16

x - 2 = √ 16

since square root has  two values it can either be positive or negative

so we have

x = 2 + √16

or

x = 2 - √16

therefore

x = 2 + √16

x = 2 + 4

x = 6

0r

x = 2 - 4

x = -2