Q. Convert the equation \(x^2-4x+3=0\). Complete the square.

Answer

To complete the square, start with

\[
x^2-4x+3=0.
\]

Move the constant:

\[
x^2-4x=-3.
\]

Complete the square on the left. Halve \(-4\) to get \(-2\), square to get \(4\):

\[
x^2-4x+4=-3+4.
\]

So

\[
(x-2)^2=1.
\]

Take square roots:

\[
x-2=\pm 1.
\]

Thus

\[
x=2\pm 1,
\]

giving

\[
x=1 \quad \text{or} \quad x=3.
\]

Detailed Explanation

We want to solve the equation by completing the square:

First, start with the given quadratic:

\[
x^2 – 4x + 3 = 0
\]

Step 1: Move the constant term to the other side

We isolate the part with \(x\) so that we can complete the square easily.

\[
x^2 – 4x = -3
\]

Step 2: Complete the square for \(x^2 – 4x\)

Recall the rule: to complete the square, take half of the coefficient of \(x\), square it, and add and subtract it appropriately.

Here, the coefficient of \(x\) in \(x^2 – 4x\) is \(-4\).

Compute half of \(-4\):

\[
\frac{-4}{2} = -2
\]

Now square \(-2\):

\[
(-2)^2 = 4
\]

So we will add and subtract \(4\) inside the expression \(x^2 – 4x\).

Rewrite the left side by grouping:

\[
x^2 – 4x + 4 – 4 = -3
\]

Group the first three terms to form a perfect square trinomial:

\[
(x^2 – 4x + 4) – 4 = -3
\]

Recognize the perfect square:

\[
(x – 2)^2 – 4 = -3
\]

Step 3: Add \(4\) to both sides

We want the square term by itself.

\[
(x – 2)^2 = -3 + 4
\]

Compute the right side:

\[
(x – 2)^2 = 1
\]

Step 4: Take the square root of both sides

If \((x – 2)^2 = 1\), then \(x – 2\) can be \(1\) or \(-1\).

\[
x – 2 = 1
\]

and

\[
x – 2 = -1
\]

Step 5: Solve each linear equation

First case:

\[
x – 2 = 1
\]

\[
x = 3
\]

Second case:

\[
x – 2 = -1
\]

\[
x = 1
\]

Final Answer

The solutions are:

\[
x = 1 \quad \text{or} \quad x = 3
\]

See full solution

Graph

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Algebra FAQ

Complete the square for \\(x^2-4x+3=0\\). What form do you get?

\\[x^2-4x+3=(x-2)^2-1\\]

Solve \\((x-2)^2-1=0\\) for \\(x\\).

\\[(x-2)^2=1\\Rightarrow x-2=\pm1\\Rightarrow x=1,3\\]

Check solutions \\(x=1\\) and \\(x=3\\) in \\(x^2-4x+3=0\\).

\\(1-4+3=0\\) and \\(9-12+3=0\\), so both work.

What is the role of \\(\\left(\\frac{-b}{2a}\\right)^2\\) for this quadratic?

Here \\(a=1,b=-4\\). Add and subtract \\(\\left(\\frac{-(-4)}{2}\\right)^2=2^2=4\\) to complete the square.

How do you rewrite \\(x^2-4x\\) as a perfect square?

\\[x^2-4x=(x-2)^2-4\\]

Why does \\(+3\\) become \\(-1\\) after completing the square?

Because \\(x^2-4x+3=(x-2)^2-4+3=(x-2)^2-1\\).
Use complete the square method. Solve x²-4x+3=0 step by step.
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