example13 := (67-47*x^3+34*x^2*y-4*x^2+31*x*y^2-81*x*y+98*x-15*y^3+42*y^2-37*y
)/(57+39*x^3-27*x^2*y+11*x^2+72*x*y^2-51*x*y-33*x+81*y^3+39*y^2+76*y)*exp((92+
78*x^3+49*x^2*y-10*x^2+61*x*y^2-57*x*y+26*x-8*y^3-4*y^2-76*y)/(24-2*x^3+64*x^2
*y-21*x^2-81*x*y^2+86*x*y+71*x-80*y^3+2*y^2+7*y));