

Equations of all the sides of a quadrilateral are given.
Now, take two adjacent equation at a time and solve it to find the point of the quadrilateral.
Let the four points are A(x1 , y1 ), B(x2 , y2 ), C(x3 , y3 ) and D(x4 , y4 ) as shown in the figure:

Now, apply formula to find equation of a line using two points and we get the equation diagonal of quadrilateral.
