How to change an symbolic equation into wanted form ?

I want to change into , how should I make it by symbolic calculation ?

syms epsilon_r epsilon_re epsilon_theta epsilon_thetae beta r r0 c c0 k
eqn4=(epsilon_r-epsilon_re)/(epsilon_theta-epsilon_thetae)==-k*beta;
epsilon_re=0;epsilon_thetae=0;
eqn5=eval(eqn4);
assume(beta,'positive')
assume(k,'positive')
eqn6=simplify(int(r^(k*beta),r,[c r])==int(r0^(k*beta),r0,[c0 r0]));
syms a a0
eqn7=subs(eqn6,[r r0],[a a0])

eqn7 =