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Solve the equation

x2 + 4x - 7 = 0
by completing the square.
Give your answers correct to 2 decimal places.​

User Zach Kemp
by
7.7k points

1 Answer

0 votes

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 = ±
√(11) ( subtract 2 from both sides )

x = - 2 ±
√(11)

Then

x = - 2 -
√(11) ≈ - 5.32 ( to 2 dec. places )

x = - 2 +
√(11) ≈ 1.32 ( to 2 dec. places )

User Tom Pickles
by
7.4k points

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