i want to solve an logarithm equation and find the value of x
log10(x^4)-log10(x^3) == log10(5*x) -log10(2*x)

4 commentaires

Davide Masiello
Davide Masiello le 11 Oct 2022
Modifié(e) : Davide Masiello le 11 Oct 2022
I believe that reduces to
and therefore there's no real solution to it
log10(4/3) == log10(5/2)
ans = logical
0
MANANJAYA NAYAK
MANANJAYA NAYAK le 11 Oct 2022
yes its there but in code how to solve and find the x value
syms a b c x
eqn = a*x^2 + b*x + c == 0
S = solve(eqn)
David Hill
David Hill le 11 Oct 2022
Use fzero to solve a non-linear equation numerically. fzero

Connectez-vous pour commenter.

 Réponse acceptée

f=@(x)log10(x.^4)-log10(x.^3)-log10(5*x) +log10(2*x);
fzero(f,2)
ans = 2.5000
x=.1:.1:10;
plot(x,f(x));

Plus de réponses (2)

if you plot, it never crosses zero.
f=@(x)log10(4*x)-log10(3*x) -log10(5*x) +log10(2*x)
f = function_handle with value:
@(x)log10(4*x)-log10(3*x)-log10(5*x)+log10(2*x)
fzero(f,1)
Exiting fzero: aborting search for an interval containing a sign change because NaN or Inf function value encountered during search. (Function value at -4.06772e+307 is -Inf.) Check function or try again with a different starting value.
ans = NaN
Torsten
Torsten le 11 Oct 2022
Modifié(e) : Torsten le 11 Oct 2022
log10(4*x)-log10(3*x) = log10((4*x)/(3*x)) = log10(4/3)
log10(5*x)-log10(2*x) = log10((5*x)/(2*x)) = log10(5/2)
So you try to "solve"
log10(4/3) = log10(5/2)
You can imagine that this makes no sense.

Catégories

Produits

Version

R2019b

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by