Let's solve the problem step by step using the information and setup provided in the image.
---
Problem Statement:
- The
length of a living room is
2 feet less than twice its width.
- The
diagonal is
2 feet more than twice the width.
- We are to find the
dimensions (width and length) of the room.
We'll use the
Pythagorean Theorem, since we're dealing with a rectangle and its diagonal.
---
Step 1: Define Variables
Let:
- $ x $ = width of the room (in feet)
- Then,
length = $ 2x - 2 $ (since it's 2 feet less than twice the width)
- Diagonal = $ 2x + 2 $ (since it's 2 feet more than twice the width)
---
Step 2: Apply the Pythagorean Theorem
For a rectangle:
$$
\text{width}^2 + \text{length}^2 = \text{diagonal}^2
$$
Substitute:
$$
x^2 + (2x - 2)^2 = (2x + 2)^2
$$
---
Step 3: Expand Each Term
First, expand $ (2x - 2)^2 $:
$$
(2x - 2)^2 = 4x^2 - 8x + 4
$$
Next, expand $ (2x + 2)^2 $:
$$
(2x + 2)^2 = 4x^2 + 8x + 4
$$
Now substitute into the equation:
$$
x^2 + (4x^2 - 8x + 4) = 4x^2 + 8x + 4
$$
Simplify left side:
$$
x^2 + 4x^2 - 8x + 4 = 5x^2 - 8x + 4
$$
So:
$$
5x^2 - 8x + 4 = 4x^2 + 8x + 4
$$
---
Step 4: Solve the Equation
Subtract $ 4x^2 + 8x + 4 $ from both sides:
$$
(5x^2 - 8x + 4) - (4x^2 + 8x + 4) = 0
$$
$$
x^2 - 16x = 0
$$
Factor:
$$
x(x - 16) = 0
$$
So:
$$
x = 0 \quad \text{or} \quad x = 16
$$
Since width can't be 0, we take:
$$
x = 16
$$
---
Step 5: Find Dimensions
-
Width = $ x = 16 $ feet
-
Length = $ 2x - 2 = 2(16) - 2 = 32 - 2 = 30 $ feet
-
Diagonal = $ 2x + 2 = 2(16) + 2 = 32 + 2 = 34 $ feet
---
Step 6: Verify Using Pythagorean Theorem
Check:
$$
16^2 + 30^2 = 256 + 900 = 1156
$$
$$
34^2 = 1156
$$
✔ It checks out!
---
✔ Final Answer:
-
Width: 16 feet
-
Length: 30 feet
-
Diagonal: 34 feet
---
Note on the Handwritten Work in Image:
The handwritten steps show:
$$
x^2 + (2x - 2)^2 = (2x + 2)^2
$$
Then incorrectly simplifies to:
$$
x^2 = (2x + 2)^2 - (2x - 2)^2
$$
Which is correct algebraically, but then the expansion is done incorrectly.
Let’s verify that approach:
$$
(2x+2)^2 - (2x-2)^2 = [4x^2 + 8x + 4] - [4x^2 - 8x + 4] = 16x
$$
So:
$$
x^2 = 16x \Rightarrow x^2 - 16x = 0 \Rightarrow x(x - 16) = 0
$$
Same result! So even though the handwriting is messy, the idea is sound — just needs careful expansion.
---
🟩 Conclusion:
The
dimensions of the room are 16 feet (width) by 30 feet (length).
Parent Tip: Review the logic above to help your child master the concept of pythagorean theorem problems worked out.