Question

What value is added to both sides of the equation x2 − 4x = −2 in order to solve by completing the square? 4, 2 , −2 , −4

Answer 1

x^2 - 4 x = -2
Add 4 to both sides:
x^2 - 4 x + 4 = 2
Write the left-hand side as a square:
(x - 2)^2 = 2
Take the square root of both sides:
x - 2 = sqrt(2) or x - 2 = -sqrt(2)
Add 2 to both sides:
x = 2 + sqrt(2) or x - 2 = -sqrt(2)
Add 2 to both sides:
Answer: x = 2 + sqrt(2) or x = 2 - sqrt(2)