Final answer:
The expression for the difference between the areas of Katie's new and old bedrooms is obtained by subtracting the area of the old bedroom (3w^2) from the area of the new bedroom ((w + 3)(3w + 4)).
Step-by-step explanation:
Understanding the Area Difference
The question asks us to find the expression representing the difference between the areas of Katie's new bedroom and her old bedroom. In Katie's old bedroom, if w represents the width, then the length is 3w since it's stated that the length is three times the width. Therefore, the area of the old bedroom is w × 3w = 3w^2.
For Katie's new bedroom, which is 4 feet longer and 3 feet wider than her old bedroom, the dimensions would be (w + 3) for the width and (3w + 4) for the length. Thus, the area of her new bedroom is (w + 3)(3w + 4).
To find the difference in area, we subtract the old area from the new area: (w + 3)(3w + 4) - 3w^2. This expression would give us the change in the area when simplified.