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Lesson: 12.2 Multiplication and Division with Polynomials
Question 3 of 13, Step 1 of 3

Erik is building a cubby bookshelf, which is a bookshelf divided into storage holes (cubbies) instead of shelves. He wants the height of the bookshelf to be [tex]\( x^2 - 5x - 6 \)[/tex] and the width to be [tex]\( x^2 + 4x + 3 \)[/tex]. Each cubby hole in the bookshelf will have a height of [tex]\( x + 3 \)[/tex] and a width of [tex]\( x - 6 \)[/tex].

Step 1 of 3: Write a rational expression to determine how many cubbies high the bookshelf will be.



Answer :

To determine how many cubbies high the bookshelf will be, we need to create a rational expression using the height of the bookshelf and the height of each cubby hole.

Given:
- Height of the bookshelf: [tex]\( x^2 - 5x - 6 \)[/tex]
- Height of each cubby hole: [tex]\( x + 3 \)[/tex]

We need to form the rational expression:
[tex]\[ \frac{\text{Height of the bookshelf}}{\text{Height of each cubby hole}} \][/tex]

First, we need to simplify the numerator (the height of the bookshelf, [tex]\( x^2 - 5x - 6 \)[/tex]):
To do this, we factor the quadratic expression.

1. Factor the quadratic expression [tex]\( x^2 - 5x - 6 \)[/tex]:

To factor [tex]\( x^2 - 5x - 6 \)[/tex], we look for two numbers that multiply to [tex]\(-6\)[/tex] (the constant term) and add up to [tex]\(-5\)[/tex] (the coefficient of [tex]\(x\)[/tex]).

The numbers [tex]\(-6\)[/tex] and [tex]\(1\)[/tex] satisfy these conditions:
[tex]\[ x^2 - 5x - 6 = (x - 6)(x + 1) \][/tex]

Now, we have:
[tex]\[ x^2 - 5x - 6 = (x - 6)(x + 1) \][/tex]

2. Simplify the rational expression:
[tex]\[ \frac{x^2 - 5x - 6}{x + 3} \][/tex]

Substitute the factored form of the numerator:
[tex]\[ \frac{(x - 6)(x + 1)}{x + 3} \][/tex]

Now, observe whether the simplified form leads to cancellation:
In this case, no common factors between the numerator [tex]\((x - 6)(x + 1)\)[/tex] and the denominator [tex]\((x + 3)\)[/tex] are identified for cancellation.

Therefore, the rational expression representing how many cubbies high the bookshelf will be:
[tex]\[ \frac{(x - 6)(x + 1)}{x + 3} \][/tex]

Hence, this is our rational expression in its simplified form.