Using MatLAB to solve 2nd Order DDE, weird output graph but not sure why?

Hi, I have an assignment for Uni to solve the 2nd Order ODE:

m*x''(t) + c*x'(t) + kx = P(t)

given initial conditions, x(t=0) = 1.0, dx/dt(t=0) = 0.0, and the values of parameters as m=1 kg, c=0.1 N•s/m, k=42 N/m , P(t)=0 N, and between 0: t : 10, and dt=0.2s,

I have a code which gives me a graph that is incorrect, however I am very new to using MATLAB and I am probably missing something obvious in my code, so any help would be very appreciated.

Code is attatched below!

Thanks!

clc;  %Clear Windows%
clear all;

f_1= @(t,V,x) -0.1*V-42*x;   %Define Functions%
f_2= @(t,V,x) V;

h=0.2;      %Define Time Step and Time Range%
t=0:h:10;

x = zeros(1,length(t));     %Create Matricies for loop%
V = zeros(1,length(t));     

x(1)=1; %Input initial conditions%
V(1)=0;

for i=1:50  %Computational loop%

      k_1_1 = h*f_1(  t(i),        x(i),            V(i));
      k_1_2 = h*f_2(  t(i),        x(i),            V(i));
      k_2_1 = h*f_1(  t(i)+h/2  ,  x(i)+k_1_1/2  ,  V(i)+k_1_2/2  );
      k_2_2 = h*f_2(  t(i)+h/2  ,  x(i)+k_1_1/2  ,  V(i)+k_1_2/2  );
      k_3_1 = h*f_1(  t(i)+h/2  ,  x(i)+k_2_1/2  ,  V(i)+k_2_2/2  );
      k_3_2 = h*f_2(  t(i)+h/2  ,  x(i)+k_2_1/2  ,  V(i)+k_2_2/2  );
      k_4_1 = h*f_1(  t(i)+h    ,  x(i)+k_3_1    ,  V(i)+k_3_2    );
      k_4_2 = h*f_2(  t(i)+h    ,  x(i)+k_3_1    ,  V(i)+k_3_2    ); 

      xn(i+1)= x(i) + (1/6)*(k_1_1+2*k_2_1+2*k_3_1+k_4_1)*h;
      x(i+1) = xn(i+1)+ (1/6)*(k_1_1+2*k_2_1+2*k_3_1+k_4_1)*h;

end

%Exact Solution%
%%%%%%%%%%%%%%%%%%%%%
A=1;
B=0.0077154;

t = 0:0.2:10;
y=A.*exp(-0.05.*t) .* cos(6.48055.*t)+B.*exp(-0.05.*t) .* sin(6.48055.*t);
%%%%%%%%%%%%%%%%%%%%%

%Graphs%

figure1 = figure;
% Create axes
axes1 = axes('Parent',figure1,'FontSize',20,'FontName','Times New Roman');
box(axes1,'on');
grid(axes1,'on');
hold(axes1,'all');
axis([axes1],[0 1 0 11]);
% Create xlabel
xlabel('t','FontSize',20,'FontName','Times New Roman');
% Create ylabel
ylabel('x','FontSize',20,'FontName','Times New Roman');
% Create multiple lines using matrix input to plot
plot1 = plot(x,t,'Parent',axes1,'LineWidth',2);
plot2 = plot(y,t,'Parent',axes1,'LineWidth',2);
%Label%
set(plot1(1),'Marker','diamond','DisplayName','RK4');
set(plot2(1),'Marker','o','Color',[1 0 0],'DisplayName','Exact');
% Create legend
legend(axes1,'show');