use symsum for equation forming and solving

I want to make a equation to slolve for variable Kd and write a code

l is index as s & c

p & and Tiijj are function of r where r is define as r_s and r_c

syms alpha s b c phi

Eq = a-b== (c-b)*(3*a+4*b)*symsum(phi_l*Tiijj(alpha_l),l,s,c) eq(1)

a = solve(Eq,a)

[Arvind]

i am confused with the expression in summation and use of symsum because Tiijj are function of Kma,Kd,K*,mu_d,mu_ma,mu* and alpha

and phi is function of alpha

alpha = [0.1 0.18 0.3];, Kma,K*,mu_ma,mu* all are constant value

and here calculate the value of Kd

[Torsten]

Don't use "symsum" in the case of only two terms in the sum.

Just write something like

syms alpha T(alpha,a) phi(alpha) a b c d 
alpha_s = 1;
alpha_c = 5;
phi(alpha) = alpha^2;
T(alpha,a) = alpha^4 + a^2;
eqn = a-b==1/3*(c-b)*(3*a+4*d)/(3*b+4*d)*(phi(alpha_s)*T(alpha_s,a)+phi(alpha_c)*T(alpha_c,a));
sol = solve(eqn,a,'MaxDegree',3)

sol = 

Answer 1

[Torsten]

The equation is linear in k_d.

So collect all terms containg k_d on the left hand side, all other terms on the right-hand side. Then factor out k_d and divide by the multiplicative factor.

[Arvind]

this is simple method i know but i confused with summation part