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The total area of two square windows is [tex]$1,025 \, \text{in}^2$[/tex]. Each side of the larger window is 5 inches longer than the sides of the smaller window. How long are the sides of the smaller window?

A. 13.5 in
B. 20 in
C. 25 in
D. 31.6 in


Sagot :

To solve this problem, let's break it down step by step.

1. Define the variables:
Let [tex]\( s \)[/tex] be the side length of the smaller window in inches.

2. Express the areas:
- The area of the smaller window is [tex]\( s^2 \)[/tex] square inches.
- The side length of the larger window is [tex]\( s + 5 \)[/tex] inches (since the larger window is 5 inches longer on each side).
- The area of the larger window is [tex]\((s + 5)^2\)[/tex] square inches.

3. Total area:
The total area of both windows combined is given as 1,025 square inches.

4. Set up the equation:
[tex]\[ s^2 + (s + 5)^2 = 1025 \][/tex]

5. Expand and simplify:
[tex]\[ s^2 + (s^2 + 10s + 25) = 1025 \][/tex]
Combine like terms:
[tex]\[ 2s^2 + 10s + 25 = 1025 \][/tex]

6. Form a quadratic equation:
[tex]\[ 2s^2 + 10s + 25 - 1025 = 0 \][/tex]
[tex]\[ 2s^2 + 10s - 1000 = 0 \][/tex]

7. Simplify the quadratic equation:
Divide every term by 2:
[tex]\[ s^2 + 5s - 500 = 0 \][/tex]

8. Solve the quadratic equation:
We can solve the quadratic equation [tex]\( s^2 + 5s - 500 = 0 \)[/tex] using the quadratic formula:
[tex]\[ s = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]
where [tex]\( a = 1 \)[/tex], [tex]\( b = 5 \)[/tex], and [tex]\( c = -500 \)[/tex].

Plug in these values:
[tex]\[ s = \frac{-5 \pm \sqrt{5^2 - 4 \cdot 1 \cdot (-500)}}{2 \cdot 1} \][/tex]
[tex]\[ s = \frac{-5 \pm \sqrt{25 + 2000}}{2} \][/tex]
[tex]\[ s = \frac{-5 \pm \sqrt{2025}}{2} \][/tex]
[tex]\[ s = \frac{-5 \pm 45}{2} \][/tex]

This gives us two potential solutions:
[tex]\[ s = \frac{40}{2} = 20 \][/tex]
[tex]\[ s = \frac{-50}{2} = -25 \][/tex]

9. Interpret the solutions:
Since a side length cannot be negative, we discard [tex]\( s = -25 \)[/tex].

Therefore, the side length of the smaller window is [tex]\( 20 \)[/tex] inches.