-30*y+30*x+2*x this is stiff ODEs, solve by runge kutta method with 50 iteration step size is 0.05. can you defined how to identify interval B/C i don't know what is interval please help me and i also need Actual solution exact values.

function yp=f(x,y)
yp=-30*y+30*x^2+2*x;   %yp=y'
x0=0; y0=1; xf=1;
n=10;
h=(xf-x0)/n;
x=x0;  y=y0;
X=x;  Y=y;
for i=1:n          %fori=1 to n do
    k1=f(x,y);     %left_hand slope     
    k2=f(x+h/2,y+h*k1/2);    %1st midpoint slope
    k3=f(x+h/2,y+h*k2/2);    %2nd midpoint slope   
    k4=f(x+h,y+h*k3);        %the right_hand slope   
    k=(k1+2*k2+2*k3+k4);    % average slope
    y=y+h*k;                %R-K step to update y  
    x=x+h;                  % updatex
    X=[X;x];                %adjoin new x-value 
    Y=[Y;y];               %adjoin new y_value
end
format long
[x,y];