Find an equation of the tangent line to the following curve at the point (0, 4).
xe^y+ye^x=4
So one wants the line equation in the form of
y= dy/dx * x + b
from the original equation..
e^y + xe^y y' + y' e^x + y e^x=0
y' (xe^y+e^y)+ y e^x + e^y=0 check that.
I would put in (0,4) and solve for y' at this point.
Then go into the line equation
y=y' x + b and solve for b at 0,4