Equation of line joining(0,0)and point of intersection of X2+Y2+2XY=4 , 3x2+5y2-xy=7 is solution) The two equations above represent pair of straight lines. We can complete the square and arrive at the 4 line equatons and find their point of intersecrtion.Simple method (by mere observation) we can say X=1&Y=1 satisfies both the equation.therfore, Line passing through origin and (1,1) is :X=Y.=>X=Y is the reqd line equation