我想問這題數學點做? 請幫幫忙!
The perimeter of a rectangular field is 36m. The width were increased by 5m and the length were decreased by 5m. The area would be decreased by 4 sq.m.
Finds its dimensions.
急問數學 quadratic equations
2009-11-27 6:25 am
回答 (1)
2009-11-27 6:33 am
✔ 最佳答案
Let the Length and Width be L m and W m respectively
Perimeter = (W + L)*2 = 36
W = 18 - L ... (1)
The area = WL = (18 - L)L
New dimension is L - 5 and W + 5
The new area = (L - 5)(W + 5)
= (L - 5)(18 - L + 5)
= (L - 5)(23 - L)
Difference in area (18 - L)L - (L - 5)(23 - L) = 4
18L - L^2 +L^2 - 28L + 115 = 4
-10L = -111
L = 11.1
Sub into (1), W = 6.9
The dimension is 11.1m x 6.9 m
收錄日期: 2021-04-23 23:19:18
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091126000051KK01579