作者alasa15 (alasa)
看板trans_math
标题Re: [考古] 积分
时间Sat May 26 10:35:38 2012
※ 引述《dreamenjoy (今天也很爽)》之铭言：
: 1.Find the number b = in (0,4) such that the line y = b divides the region
: bounded by the curves y = x^2 and y = 4 into two regions with equal area
: 4
: ---
: 3
: 我算答案是2 不知道有无错误
: 有高手能帮解答吗?
: 我做法是令上半面积等於下半面积来求解
x
|
2| - x=√y
| -
| -
| -
|-
----------------y
b 4
变成这样应该满好做的(利用了对称性)
b 4
∫√y dy = ∫√y dy
0 b
b^1.5 = 4^1.5 - b^1.5 = 8 - b^1.5
=> b^1.5 = 4
=> b = 4^(2/3) = 2^(4/3)
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