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solve value in matrix form

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Sheryl
Sheryl 2013-3-10
关闭： MATLAB Answer Bot 2021-8-20
I have a set of value, i'm trying to use matlab to calculate the value by set, however i cant get matlab to work with it with the code i generated.
this is the code i use, where c=[1 2 3 5], t=[5 9 7 6],
double( solve(c*(y*exp(-t/y)) ), y ) )
how cant i get y in a set of value?

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回答（1 个）

Walter Roberson
Walter Roberson 2013-3-10
syms c t y
fun = matlabFunction( solve( c*(y*exp(-t/y)), y ), 'vars', {c t});
fun([1 2 3 5], [5 9 7 6])
  2 个评论
Sheryl
Sheryl 2013-3-11
why i always get this comment when i try out the code?
Warning: Explicit solution could not be found. > In solve at 169
is there anything wrong with my code?
Walter Roberson
Walter Roberson 2013-3-12
exp(-t/y) is non-zero provided that -t/y is not -infinity.
y times a value is zero only if y is 0 or the value is 0.
So when is -t/y equal to -infinity? Never.
So for c * y*exp(-t/y) to be 0 with non-zero c, y must be 0, to get the y* part to be 0. But when it is, we have exp(-t/0) which is division by 0 which is undefined. And 0 times undefined is undefined.
Thus there is no value for which c * y * exp(-t/y) is 0 for finite non-zero c and t, so solve() must say that no solutions can be found.

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