X*X = X+X+X.....+X
(X*X)' = X'+ X'+X'.....+X'
2X = 1+1+1......+1
2X = X
2 = 1
错在哪儿
the first line is wrong. If it holds, the x must be a integer. The following derivative is not justified. |
To find the problem, see the following: Let x =1. Then x'=1', that is, 1 = 0. |
For a given equation 1, the number of term on the left side is GIVEN, as X (X= integer, can be 0 to infinity). So X here is a number, not a variable. Taking derivative of the both sides of equation 1 will yield 0 = 0+0+0.....+0 so 0 =0 本贴由[salmonfish]最后编辑于:2008-9-18 22:18:8 |
只有在X不等于0的前提下,才可以在等式两端同时除以X;即使假定X不等于0,从第二步到第三步也不成立。第三个等式应该写成: (X<>0) X=1+1+....+1 |
答案呢???!!!! |
右边求导过程出错。因为 X+X+X.....+X 的项数依赖于X,函数和的求导公式不能用,即 (X+X+X+...+X)'¹X'+X'+X'+...+X'。 |
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