#y=ln(8x^2+9y^2)#
#dy/dx=(16x)/(8x^2+9y^2)+(18y)/ (8x^2+9y^2) dy/dx#
#dy/dx -(18y)/ (8x^2+9y^2) dy/dx=(16x)/(8x^2+9y^2)#
#dy/dx(1-(18y)/ (8x^2+9y^2) )=(16x)/(8x^2+9y^2)#
#dy/dx((8x^2+9y^2-18y)/ (8x^2+9y^2) )=(16x)/(8x^2+9y^2)#
#dy/dx=((16x)/(8x^2+9y^2))/((8x^2+9y^2-18y)/ (8x^2+9y^2) )#
#dy/dx=(16x)/(8x^2+9y^2-18y)#