Problem on solving with dsolve

I'm having trouble using dsolve to solve a DE using 2 strategies. I'm getting different answers. Please advise. NOte: warning doesn't botter me.

% FILE: test.m

% Solving an ODE (RLC circuit response) with innitial conditions. Example 2.29 from Kalechman

% Pratical Matlab applications for engineers pag 196

% equation: (1/36)*D2y+(1/9)*Dy+(1/9)*y=0

% initial conditions: y(0) = 0 and Dy(0)= 432

% solution: 432*t*exp(-2*t)

% 2 differente strategies using dsolve with explot or fplot;

clear; sym eq;

% strategy #1 - works fine but with warning

% using a single string and call dsolve

% solution (correct, OK): 432*t*exp(-2*t)

% model = dsolve('(1/36)*D2y+(1/9)*Dy+(1/9)*y=0','y(0) = 0','Dy(0)= 432','t')

% strategy #2 - works, different answer and includes warning

% build equation in one outside string and call dsolve

% eq=strcat('1/36','*D2y+','1/9','*Dy+','1/9','=0')

% eq = '1/36' + '*D2y+' + '1/9' + '*Dy+' + '1/9' + '=0' % gives error

eq='1/36*D2y+1/9*Dy+1/9=0'; % solution (wrong, NOK): 433/4 - (433*exp(-4*t))/4 - t

model=dsolve(eq,'y(0) = 0','Dy(0)= 432','t')

% plotting

figure(1)

% ezplot(model); % or

fplot(model);

xlabel('t(s)')

ylabel('v(volts)')

title('v(t) vs t')

axis([0 6 0 90]);

Answer 1

[Dyuman Joshi]

You got the wrong result because your equation is wrong, you forgot to include '*y' in the 3rd approach.

eq=strcat('1/36','*D2y+','1/9','*Dy+','1/9','*y','=0')

eq = '1/36*D2y+1/9*Dy+1/9*y=0'

model=dsolve(eq,'y(0) = 0','Dy(0)= 432','t')

Warning: Support of character vectors and strings will be removed in a future release. Use sym objects to define differential equations instead.

model = 

And as the warning suggest, it is best to use sym objects rather than char vectors and strings.