>> syms x y
>> z=28544953854119202593525972496744320000/1427247692705960025784236001705007*y+5534023222112865484800/73786976294838200321+856348615623575889883579789414527664128000/1427247692705960025784236001705007*x^2*y-221360928884514619392000000/73786976294838200321*x^2+285449538541192023740817577202967956684800/1427247692705960025784236001705007*y^3