A student's work is shown below.
[tex]\[
\begin{array}{l}
\sqrt{6 x-11}+3=x \\
\sqrt{6 x-11}=x-3 \\
(\sqrt{6 x-11})^2=(x-3)^2 \\
6 x-11=x^2-6 x+9 \\
0=x^2-12 x+20 \\
0=(x-2)(x-10) \\
x-2=0 \quad x-10=0 \\
x=2 \\
x=10 \\
\end{array}
\][/tex]

Which of the statements is true?

A. The student incorrectly factored the polynomial [tex]\(x^2-12x+20\)[/tex].

B. The student incorrectly expanded the binomial [tex]\((x-3)^2\)[/tex].

C. The student included an extraneous solution of [tex]\(x=2\)[/tex]. The correct solution is [tex]\(x=10\)[/tex] only.

D. The student's work is correct.



Answer :

The student's work is mostly correct. Let's go through the solution step-by-step to identify any potential errors or extraneous solutions.

Given the equation:
[tex]\[ \sqrt{6x - 11} + 3 = x \][/tex]

1. Isolate the square root term:
[tex]\[ \sqrt{6x - 11} = x - 3 \][/tex]

2. Square both sides to eliminate the square root:
[tex]\[ (\sqrt{6x - 11})^2 = (x - 3)^2 \][/tex]
[tex]\[ 6x - 11 = x^2 - 6x + 9 \][/tex]

3. Rearrange the equation to form a standard quadratic equation:
[tex]\[ 0 = x^2 - 6x + 9 - 6x + 11 \][/tex]
[tex]\[ 0 = x^2 - 12x + 20 \][/tex]

4. Factorize the quadratic equation:
[tex]\[ 0 = (x - 2)(x - 10) \][/tex]

5. Solve for [tex]\( x \)[/tex]:
[tex]\[ x - 2 = 0 \quad \Rightarrow \quad x = 2 \][/tex]
[tex]\[ x - 10 = 0 \quad \Rightarrow \quad x = 10 \][/tex]

Now, it's important to check for extraneous solutions by substituting the values back into the original equation:
1. For [tex]\( x = 2 \)[/tex]:
[tex]\[ \sqrt{6(2) - 11} + 3 = 2 \][/tex]
[tex]\[ \sqrt{12 - 11} + 3 = 2 \][/tex]
[tex]\[ \sqrt{1} + 3 = 2 \][/tex]
[tex]\[ 1 + 3 \neq 2 \][/tex]
So, [tex]\( x = 2 \)[/tex] is not a valid solution.

2. For [tex]\( x = 10 \)[/tex]:
[tex]\[ \sqrt{6(10) - 11} + 3 = 10 \][/tex]
[tex]\[ \sqrt{60 - 11} + 3 = 10 \][/tex]
[tex]\[ \sqrt{49} + 3 = 10 \][/tex]
[tex]\[ 7 + 3 = 10 \][/tex]
This holds true, so [tex]\( x = 10 \)[/tex] is a valid solution.

Therefore, the correct statement is:
The student included an extraneous solution of [tex]\( x = 2 \)[/tex]. The correct solution is [tex]\( x = 10 \)[/tex] only.