Complete the square f(x)=x^2-12x-4

Solve for x over the real numbers:

x^2 - 12 x - 4 = 0

Add 4 to both sides:

x^2 - 12 x = 4

Add 36 to both sides:

x^2 - 12 x + 36 = 40

Write the left hand side as a square:

(x - 6)^2 = 40

Take the square root of both sides:

x - 6 = 2 sqrt(10) or x - 6 = -2 sqrt(10)

Add 6 to both sides:

x = 6 + 2 sqrt(10) or x - 6 = -2 sqrt(10)

Add 6 to both sides:

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| x = 6 + 2 sqrt(10) or x = 6 - 2 sqrt(10)