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[quote]原帖由 [i]好望角234[/i] 於 2022-9-14 00:52 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=552048708&ptid=30765503][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]
[img]https://img.discuss.com.hk/d/attachments/day_220914/20220914_53381c21b58b296d0472dEGtQWD7khDg.jpg[/img] [/quote]
A = x(90-3x/2)
Consider A = 1134,
90x - 3x²/2 = 1134
3x² - 180x + 2268 = 0
x² - 60x + 756 = 0
(x-42)(x-18) = 0
x = 18 or 42

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[quote]原帖由 [i]法律領導班子[/i] 於 2022-9-15 14:41 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=552092974&ptid=30765503][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]
y = (90 - x - x)
A = x  * y
x = 21, y = 48 ,  A = 1008

x = 22 , y = 46  , A = 1012
x = 23 , y = 44  , A = 1012
x = 24 , y = 42,  A = 1008


A can not be 1134 cm2 [/quote]
I think y = (180-3x)/2

[quote]原帖由 [i]好望角234[/i] 於 2022-9-14 00:52 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=552048708&ptid=30765503][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]
[img]https://img.discuss.com.hk/d/attachments/day_220914/20220914_53381c21b58b296d0472dEGtQWD7khDg.jpg[/img] [/quote]
1. 180cm = 3X + 2L
2. A = X*L

A 可吾可以= 1134 平方CM ?

1.
180 = 3X + 2L
180-3X = 2L
L = (180-3X)/2

2.
A = X * L
A= X * (180-3X) / 2
A = (180X - 3X^2) / 2
A = 90X - 3/2*X^2

如果 A = 1134 = 90X - 3/2X^2
1134 = 90X - 3/2X^2
3/2X^2 - 90X + 1134 = 0

考慮 : aX^2 + bX + c = 0
求出 X 是否合理便可以確認 A = 1134 是否可行。

[url]https://en.wikipedia.org/wiki/Quadratic_formula[/url]