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Julian factored the expression [tex]$2x^4 + 2x^3 - x^2 - x$[/tex]. His work is shown below. At which step did Julian make his first mistake, and which statement describes the mistake?

\begin{tabular}{|l|l|}
\hline
& [tex]$2x^4 + 2x^3 - x^2 - x$[/tex] \\
\hline
Step 1 & [tex]$= x(2x^3 + 2x^2 - x - 1)$[/tex] \\
\hline
Step 2 & [tex]$= x[2x^2(x + 1) - 1(x - 1)]$[/tex] \\
\hline
Step 3 & [tex]$= x(2x^2 - 1)(x + 1)(x - 1)$[/tex] \\
\hline
\end{tabular}

\begin{tabular}{|l|l|}
\hline
Statement 1 & Julian should have factored [tex]$(2x^2 - 1)$[/tex] as a difference of squares. \\
\hline
Statement 2 & Julian incorrectly applied the distributive property when factoring out -1. \\
\hline
Statement 3 & Julian should have factored [tex]$2x$[/tex] from all terms instead of [tex]$x$[/tex]. \\
\hline
Statement 4 & Julian incorrectly factored [tex]$2x^2$[/tex] from the first group of terms. \\
\hline
\end{tabular}


Sagot :

Let's analyze the given problem step-by-step to determine where Julian made his first mistake in factoring the expression [tex]\(2x^4 + 2x^3 - x^2 - x\)[/tex].

Start from the original expression:
[tex]\[ 2x^4 + 2x^3 - x^2 - x \][/tex]

### Step 1
Julian factors out [tex]\(x\)[/tex] from the expression:
[tex]\[ 2x^4 + 2x^3 - x^2 - x = x(2x^3 + 2x^2 - x - 1) \][/tex]

This step is correct.

### Step 2
Julian attempts to further factor the expression inside the parenthesis:
[tex]\[ x(2x^3 + 2x^2 - x - 1) = x\left[2x^2(x + 1) - 1(x - 1)\right] \][/tex]

Here, we should carefully verify the factorized form. Julian's step introduces a mistake because let's see what happens if we expand his factorization:

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

Comparing this with the original expression inside the parenthesis [tex]\(2x^3 + 2x^2 - x - 1\)[/tex], we see that they don't match since the last term [tex]\(+1\)[/tex] doesn't match [tex]\(-1\)[/tex].

Julian made an error in applying the distributive property when considering [tex]\( -1(x - 1) \)[/tex]. The correct factorization should have been:
[tex]\[ 2x^2(x + 1) - 1(x + 1) = (2x^2 - 1)(x + 1) \][/tex]

### Step 3
Julian proceeds with his mistaken expression:
[tex]\[ x\left(2x^2 - 1\right)(x + 1)(x - 1) \][/tex]

But because the mistake was in Step 2, this step follows the faulty logic from Step 2.

### Conclusion
The first mistake was in Step 2. The correct statement describing this mistake is:
[tex]\[ \text{Statement 2: Julian incorrectly applied the distributive property when factoring out -1} \][/tex]

Thus, Julian's error was in Step 2, and it was due to incorrect application of the distributive property when factoring out [tex]\(-1\)[/tex].