F.4 Maths
回答 (2)
2011-12-18 2:20 am
✔ 最佳答案
設2年前車子的價值是x﹐則現在的價值是0.68x據題意0.68x = x * r% * (r - 5)%
0.68 = r(r - 5)/100^2
6800 = r(r - 5)
r = 85
2011-12-18 2:26 am
let P be the price 2 years ago
last year: L = P(r%)
now: N = L(r-5)% = P(r%)(r-5)% = P(68%)
(r%)(r-5)% = 68%
(r/100) [(r-5)/100] = 68/100
r [(r-5)/100] = 68
r^2 - 5r = 6800
r^2 - 5r - 6800 = 0
(r-85)(r+80) = 0
r = 85 or -80 (neglected)
last year: L = P(r%)
now: N = L(r-5)% = P(r%)(r-5)% = P(68%)
(r%)(r-5)% = 68%
(r/100) [(r-5)/100] = 68/100
r [(r-5)/100] = 68
r^2 - 5r = 6800
r^2 - 5r - 6800 = 0
(r-85)(r+80) = 0
r = 85 or -80 (neglected)
收錄日期: 2021-04-11 18:49:29
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20111217000051KK00666