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Solve the quadratic equation by completing the square.

[tex]\( 0 = x^2 - 6x + 4 \)[/tex]

[tex]\[
\begin{array}{l}
-4 = x^2 - 6x \\
-4 + 9 = x^2 - 6x + 9 \\
5 = (x - 3)^2
\end{array}
\][/tex]

What are the two solutions of the equation?

A. [tex]\( x = 3 + \sqrt{5} \)[/tex] and [tex]\( x = 3 - \sqrt{5} \)[/tex]

B. [tex]\( x = \sqrt{5} \)[/tex] and [tex]\( x = -\sqrt{5} \)[/tex]

C. [tex]\( x = 5 + \sqrt{3} \)[/tex] and [tex]\( x = 5 - \sqrt{3} \)[/tex]

D. [tex]\( x = \sqrt{\frac{5}{3}} \)[/tex] and [tex]\( x = -\sqrt{\frac{5}{3}} \)[/tex]


Sagot :

To solve the quadratic equation [tex]\(0 = x^2 - 6x + 4\)[/tex] by completing the square, let's go through the solution step-by-step:

1. Start with the original equation:
[tex]\[ 0 = x^2 - 6x + 4 \][/tex]

2. Rewrite the equation by isolating the quadratic and linear terms on one side:
[tex]\[ x^2 - 6x = -4 \][/tex]

3. To complete the square, we need to add and subtract the square of half the coefficient of [tex]\(x\)[/tex]. The coefficient of [tex]\(x\)[/tex] here is [tex]\(-6\)[/tex], so half of it is [tex]\(-3\)[/tex], and squaring it gives [tex]\(9\)[/tex]:
[tex]\[ x^2 - 6x + 9 = -4 + 9 \][/tex]

4. Now, our equation looks like this:
[tex]\[ (x - 3)^2 = 5 \][/tex]

5. Next, take the square root of both sides of the equation:
[tex]\[ \sqrt{(x - 3)^2} = \sqrt{5} \][/tex]

6. This gives us two possible equations since [tex]\((x - 3)\)[/tex] can be positive or negative:
[tex]\[ x - 3 = \sqrt{5} \][/tex]
[tex]\[ x - 3 = -\sqrt{5} \][/tex]

7. Solving these equations for [tex]\(x\)[/tex] gives:
[tex]\[ x = 3 + \sqrt{5} \][/tex]
[tex]\[ x = 3 - \sqrt{5} \][/tex]

Thus, the two solutions of the quadratic equation [tex]\(0 = x^2 - 6x + 4\)[/tex] are:
[tex]\[ x = 3 + \sqrt{5} \][/tex]
[tex]\[ x = 3 - \sqrt{5} \][/tex]

So the correct answer is:
[tex]\[ x = 3 + \sqrt{5} \text{ and } x = 3 - \sqrt{5} \][/tex]