Answer:
x ≈ - 5.32, x ≈ 1.32
Explanation:
Given
x² + 4x - 7 = 0 ( add 7 to both sides )
x² + 4x = 7
To complete the square
add ( half the coefficient of the x- term )² to both sides
x² + 2(2)x + 4 = 7 + 4
(x + 2)² = 11 ( take the square root of both sides )
x + 2 = ±
( subtract 2 from both sides )
x = - 2 ±

Hence
x = - 2 -
≈ - 5.32
x = - 2 +
≈ 1.32