y varies directly as x+9 and inversely as √z where z＞0, y=13 when x=17 and z=16.
(a) Express y in terms of x and z
(b) Find the value of x when y=3 and z=64(c) If x is fixed and z decreases by 75%, find the percentage change in y.
F.4 variations~
2010-01-23 7:53 am
回答 (1)
2010-01-23 8:09 am
✔ 最佳答案
(a) y = k(x+9)/√z where k is a constant13 = k(17+9)/√16
13 = 26k/4
k = 2
Hence, y = 2(x+9)/√z
(b) when y = 3, z = 64,
3 = 2(x+9)/√64
24 = 2(x + 9)
12 = x + 9
x = 3
(c) y = 2(x+9)/√z
If z is decreased by 75%, new value of z = (1-0.75)z = 0.25z
New value of y = 2(x+9)/ √(0.25z)
= 2(x+9)/[0.5√z] = 2y
= 2 * 2(x+9)/√z = 2y
Hence y is increased by (2y – y)/y * 100% = 100%
收錄日期: 2021-04-13 17:03:24
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100122000051KK01715