Question

How to complete the square of: 3x^2-6x-12=0

Answer 1

exact form:

x=±√5+1

decimal form:

x = 3.23606797..., -1.23606797...

Explanation:

Use the formula (b/2)^2 in order to create a new term. Solve for x by using this term to complete the square. ---- :))

Answer 2

x = √5 + 1, x = -√5 + 1

Explanation:

We want the coefficient of x^2 to be 1, so let's divide either side by 3;

3x^2 - 6x - 12 = 0 => Divide either side by 3

3x^2/3 - 6x/3 - 12/3 = 0/3 => Simplify

x^2 - 2x - 4 = 0

Let's try to form a perfect square;

(x^2 - 2x + ? ) - 4 = 0

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1/2(- 2) = (- 1)^2 = 1

(x^2 - 2x + 1) + 4 - 1 = 0

(x - 1)^2 - 5 = 0

(x - 1)^2 = 5

For x - 1 = √5 : x = √5 + 1

For x - 1 = - √5 : x = -√5 + 1