<h3>
Answer: 16 ft by 25 ft</h3>
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Explanation:
Refer to the diagram below.
The outer dimensions 24 ft and 33 ft shrink down to 24-2x ft and 33-2x ft respectively. This subtraction of 2x is due to subtracting two copies of x per side.
The carpet has area of (24-2x)(33-2x)
Cynthia can afford to buy 400 sq ft of carpet
So we set 400 equal to that previous expression and solve for x
(24-2x)(33-2x) = 400
24(33-2x) - 2x(33-2x) = 400
792-48x - 66x + 4x^2 = 400
4x^2 - 114x + 792 = 400
4x^2 - 114x + 792-400 = 0
4x^2 - 114x + 392 = 0
From here, use the quadratic formula to isolate x.
Plug in a = 4, b = -114, c = 392
![x = \frac{-b\pm\sqrt{b^2-4ac}}{2a}\\\\x = \frac{-(-114)\pm\sqrt{(-114)^2-4(4)(392)}}{2(4)}\\\\x = \frac{114\pm\sqrt{6724}}{8}\\\\x = \frac{114\pm82}{8}\\\\x = \frac{114+82}{8} \ \text{ or } \ x = \frac{114-82}{8}\\\\x = \frac{196}{8} \ \text{ or } \ x = \frac{32}{8}\\\\x = 24.5 \ \text{ or } \ x = 4\\\\](https://tex.z-dn.net/?f=x%20%3D%20%5Cfrac%7B-b%5Cpm%5Csqrt%7Bb%5E2-4ac%7D%7D%7B2a%7D%5C%5C%5C%5Cx%20%3D%20%5Cfrac%7B-%28-114%29%5Cpm%5Csqrt%7B%28-114%29%5E2-4%284%29%28392%29%7D%7D%7B2%284%29%7D%5C%5C%5C%5Cx%20%3D%20%5Cfrac%7B114%5Cpm%5Csqrt%7B6724%7D%7D%7B8%7D%5C%5C%5C%5Cx%20%3D%20%5Cfrac%7B114%5Cpm82%7D%7B8%7D%5C%5C%5C%5Cx%20%3D%20%5Cfrac%7B114%2B82%7D%7B8%7D%20%5C%20%5Ctext%7B%20or%20%7D%20%5C%20x%20%3D%20%5Cfrac%7B114-82%7D%7B8%7D%5C%5C%5C%5Cx%20%3D%20%5Cfrac%7B196%7D%7B8%7D%20%5C%20%5Ctext%7B%20or%20%7D%20%5C%20x%20%3D%20%5Cfrac%7B32%7D%7B8%7D%5C%5C%5C%5Cx%20%3D%2024.5%20%5C%20%5Ctext%7B%20or%20%7D%20%5C%20x%20%3D%204%5C%5C%5C%5C)
The two possible solutions are x = 24.5 and x = 4
But if x = 24.5, then 24 - 2x = 24 - 2*24.5 = -25 which isn't possible. We cannot have a negative width or negative length for the carpet.
Luckily x = 4 does work since
24 - 2x = 24 - 2*4 = 16
33 - 2x = 33 - 2*4 = 25
Both results are positive.
Therefore, the carpet has dimensions of <u>16 ft by 25 ft</u>
Check: 16*25 = 400, so the answer is confirmed