||'''Book'''|| Getting started with MATLAB ||
 ||'''Author'''|| Rudra Pratap ||
 ||'''Edition'''||  ||

/* code_begins */

{{{
sage: x,y,z=var('x,y,z')
sage: contour_plot(-1/2*x**2+x*y+y**2,(x,-5,5),(y,-5,5))


}}}

/* code_ends */

 * '''Solution by''': 
   * < VINAY >, < STUDENT >, < Symbiosis >
   * <Your Name>, <Profession>, <Organization>