If xy+x+y=1, find dy/dx.
use implicit differentiation, and the product and chain rules.
(xy)' + x' + y' = (1)'
y + xy' + 1 + y' = 0
y'(x+1) = -(y+1)
y' = -(y+1)/(x+1)
(xy)' + x' + y' = (1)'
y + xy' + 1 + y' = 0
y'(x+1) = -(y+1)
y' = -(y+1)/(x+1)