How to solve single non-linear equation?
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ISHA ARORA
on 21 Sep 2021
Commented: ISHA ARORA
on 24 Sep 2021
Can anyone please help in solving the following equation:
d/dt[V.(X/1-X)]= An-Ax-Bx
where, V and X are function of t.
A,B, and n are constants
2 Comments
Accepted Answer
Walter Roberson
on 21 Sep 2021
syms A B n X(t) V(t)
eqn = diff(V(t) .* X(t)/(1-X(t)), t) == A*n - A*X(t) - B*X(t)
SE = simplify(lhs(eqn) - rhs(eqn))
collect(SE, X(t))
dsolve(ans)
You do not have a single linear equation. You are taking the derivative of a multiple of function V and function X and that is something that cannot be resolved by itself.
3 Comments
Walter Roberson
on 22 Sep 2021
Please confirm that what you are taking the derivative of on the left side is the product of two unknown functions in t.
If so, then my understanding is the situation cannot be resolved -- in much the same way that you cannot solve a single equation in two variables except potentially down to finding a relationship between the variables.
In some cases it can be resolved. For example, if V(t) is known to be linear
syms A B n X(t) V(t) C2 C1 C0
V(t) = C1*t + C0
eqn = diff(V(t) .* X(t)/(1-X(t)), t) == A*n - A*X(t) - B*X(t)
SE = simplify(lhs(eqn) - rhs(eqn))
col = collect(SE, X(t))
sol = simplify(dsolve(col))
... which is independent of time. Extending V(t) to quadratic gives you a situation dsolve() is not able to resolve.
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