xy³+2x²y-x+1=0
y³+x·3y²·y'+4xy+2x²·y'-1=0
(3xy²+2x²)·y'=1-y³-4xy
y'=(1-y³-4xy)/(3xy²+2x²)
dy/dx=(1-y³-4xy)/(3xy²+2x²)