im tryng to solve it with the solver [t y] =ode45(@problem1,[0 50],[0 30]) but is not working

function [xprimes]=problem1(t,x)
m= .25;
C=.03;
g=9.800665;

xprimes=[ x(3); y(3);-((C*x(2))/m)*(sqrt(x(2)^2+y(2)^2)); -g-(C/m)*y(2)*sqrt(x(2)^2+y(2)^2)];
end

[Star Strider]

You have not defined ‘y’.