梯形既周界點計嫁

2007-09-02 11:18 pm
上底係 x - 1
下底係 x - 3
高係 8
斜個條係 9
設已知梯形的周界為 P
( a ) 求一與 P 有關的公式
( b ) 若周界是57 ,求一對平行邊的總長度


請大家幫的計下
唔該!!!!!!!!
更新1:

唔好意思呀 打錯野呀 下底係x + 3呀

回答 (2)

2007-09-02 11:23 pm
✔ 最佳答案
梯形得四條邊 , 加哂佢就係周界

(a)
P = (x-1) + (x-3) +8 + 9
P = 2x +13

(b)
P = 57
57 = 2x +13
2x = 44
x = 22
平行邊的總長度 = (x-1) + (x-3) = 21 + 19 = 40

2007-09-02 22:13:41 補充:
唔緊要 , 我地實識做 , 改少少就可以了最緊要個方法你明白 , 自己做到(a)P = (x-1) (x 3) 8 9P = 2x 19(b)P = 5757 = 2x 192x = 38x = 19平行邊的總長度 = (x-1) (x 3) = 18 22 = 40
2007-09-03 11:56 pm
a. P=(x-1)+(x+3)+9+9
=x-1+x+3+18
=2x+20
b. 2x+20=57
2x=37
x=18.5
57-9-9
=39
參考: me


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