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I need the Solution of this equation

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dashty
dashty 2013-3-3
关闭： MATLAB Answer Bot 2021-8-20
If
E=1:0.5:10;
A=2.5;
B=3.18;
C=4.25;
D=0.15;
then
S = A + B*(lnE/E)+ C*(lnE/E)^2 + D*(E/lnE)

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回答（6 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-3-3
syms A B C D E lnE
s=solve(A + B*(lnE/E)+ C*(lnE/E)^2 + D*(E/lnE),lnE)
E=1:0.5:10;
A=2.5;
B=3.18;
C=4.25;
D=0.15;
out=subs(s)
Youssef Khmou
Youssef Khmou 2013-3-3
hi,
A=2.5;
B=3.18;
C=4.25;
D=0.15;
f=@(E) A + B.*(log(E)./E)+ C.*(log(E)./E).^2 + D*(E./log(E))
E=1:0.5:10;
figure, fplot(f,E)
fsolve(f,0)
Matt J
Matt J 2013-3-3
编辑：Matt J 2013-3-3
I need to fill in a few blanks for myself. If I assume that E is the unknown to solve for (your post seems to say it is a vector of data) and S is supposed to be zero (your post doesn't specify), then there are no real solutions. Your equation is quadratic in lnE/E with roots
>> r=roots([C,B-D,A])
r =
-0.3565 + 0.6791i
-0.3565 - 0.6791i
dashty
dashty 2013-3-4
sorry but no one answered correctly
  3 个评论
显示 1更早的评论
dashty
dashty 2013-3-4
Dear Azzi thank you for your interest my equation is
S = A + B*(lnE/E)+ C*(lnE/E)^2 + D*(E/lnE)
if A ,B,C,D is constants as the following
A=2.5;
B=3.18;
C=4.25;
D=0.15;
so we want do determine the value of S for all E
and E = (1,2,3,4,5,6,7,8,9,10)
Jan
Jan 2013-3-4
@dashty: "no answer is correctly" is not helpful. 1. It is not clear which answer are concerned by this question, because some answers could be posted afterwards. Of course I can compare the date and time of the answers manually, but this wastes the time of all who want to help you. 2. Instead of mentioning, that they are not correct, a detailed description between the results and your expectations would help to improve the answers. Currently the quality of the answers exceed the information density of the question. Please do not let us guess, what you want.
Matt J
Matt J 2013-3-4
编辑：Matt J 2013-3-4
f=@(E) A + B.*(log(E)./E)+ C.*(log(E)./E).^2 + D*(E./log(E))
S=f(1:10);
Azzi Abdelmalek
Azzi Abdelmalek 2013-3-4
This is not an equation:
A=2.5;
B=3.18;
C=4.25;
D=0.15;
E=1:10
S=A + B*(log(E)./E)+ C*(log(E)./E).^2 + D*(E./log(E))

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