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Jane evaluates [tex]$x^2 - 3x + 5$[/tex] for [tex]$x = -2$[/tex] below.

Step 1: [tex]$(-2)^2 - 3(-2) + 5$[/tex]
Step 2: [tex] = 4 + 6 + 5[tex]$[/tex]
Step 3: [tex] = 15$[/tex][/tex]

What, if any, was Jane's mistake?

A. Jane made no mistakes.
B. Jane incorrectly evaluated [tex]$(-2)^2$[/tex] in step 2.
C. Jane incorrectly added the terms in step 3.
D. Jane incorrectly substituted [tex]x = -2[/tex] in step 1.


Sagot :

Let's carefully evaluate the expression [tex]\( x^2 - 3x + 5 \)[/tex] step-by-step for [tex]\( x = -2 \)[/tex] and identify any possible mistakes Jane may have made.

### Step 1: Substitution
We substitute [tex]\( x = -2 \)[/tex] into the expression.

[tex]\[ (-2)^2 - 3(-2) + 5 \][/tex]

So far, the substitution has been done correctly.

### Step 2: Evaluation of each term
Evaluate [tex]\( (-2)^2 \)[/tex], [tex]\( -3(-2) \)[/tex], and [tex]\( + 5 \)[/tex]:

[tex]\[ (-2)^2 = 4 \][/tex] (since squaring a negative number results in a positive number)
[tex]\[ -3(-2) = 6 \][/tex] (since multiplying two negative numbers results in a positive number)
[tex]\[ + 5 \][/tex] remains the same.

Putting it all together:

[tex]\[ 4 + 6 + 5 \][/tex]

### Step 3: Add the terms

Now, let's add the evaluated terms:

[tex]\[ 4 + 6 = 10 \][/tex]
[tex]\[ 10 + 5 = 15 \][/tex]

Therefore,

[tex]\[ 4 + 6 + 5 = 15 \][/tex]

### Identifying Jane's Mistake

Jane had in her Step 2:

[tex]\[ = -4 + 6 + 5 \][/tex]

This appears to be incorrect because she evaluated [tex]\( (-2)^2 \)[/tex] as [tex]\(-4\)[/tex] instead of [tex]\(4\)[/tex].

In her Step 3:

[tex]\[ = 7 \][/tex]

Jane added the terms incorrectly because the correct sum [tex]\( 4 + 6 + 5 \)[/tex] should yield [tex]\( 15 \)[/tex], not [tex]\( 7 \)[/tex].

Thus, Jane actually made two mistakes:
1. Incorrectly evaluated [tex]\( (-2)^2 \)[/tex] as [tex]\(-4\)[/tex] instead of [tex]\(4\)[/tex].
2. Incorrectly added the terms.

Given the multiple-choice nature of the problem and focusing on the key mistake:
Jane incorrectly added the terms in step 3.

Hence, the answer is:
- Jane incorrectly added the terms in step 3.

So, that would be noted as:

Jane incorrectly added the terms in step 3.
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