# Solve the quadratic equation x2 + 4x – 5 = 0 by the method of completing the square.

x2 + 4x – 5 = 0

x2 + 4x = 5

Now by taking half of the coefficient of x and then squaring it and adding on both LHS and RHS sides.

Coefficient of x = 4

Half of 4 = 2

Squaring the half of 4 = 4

x2 + 4x + 4= 5 + 4

(x + 2)2 = 9

On simplifying both RHS and LHS we get an equation of following form,

(x ± A)2 = k2

Taking square root of both sides,

(x + 2) = ±3

Solving first with positive sign of 3,

x + 2 = 3

x = 3 – 2

x = 1

Solving with negative sign of 3,

x + 2 = -3

x = -3 – 2

x = -5

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