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[中华] 求助解数学题

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niff

2014-9-9 11:32 AM

本帖最后由 niff 于 2014-9-9 11:39 AM 编辑

(X-10%)-20%=108
我想要全部步骤。感激不尽

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[D]-KY

2014-9-9 01:23 PM

首先，请表明10%是x的10%还是1的10%
另外请表明那个20% 是（x- 10%) * -20%（乘）还是 -20%（减）

assumption(减）10% = x*10% & 20% = x*20%
[x - x(10%)]-x(20%)= 108
x - 0.1x - 0.2x = 108
x - 0.3x = 108
0.7x = 108
x = 108/0.7
x approximates to 154.286

assumption（乘）10% = x*10% & 20% = x*20%
[x - x(10%)]*[-x(20%)]= 108
(x-0.1x)*(-0.2x) = 108
(0.9x)*(-0.2x) = 108
-0.18x^2 = 108
x^2 = -600
x = i[sqrt(600)]

assumption(减）10% = 1*10% & 20 = 1*20%
(x-0.1)-0.2 = 108
x - 0.3 = 108
x = 108.3

assumption(乘）10% = 1*10% & 20 = 1*20%
(x-0.1)*(-0.2) = 108
-0.2x + 0.02 = 108
-0.2x = 107.98
x = -539.9