Suppose 4y + xy = 2. Evaluate d^2x/d2^y at the point (-3, 2).

x = (2-4y)/y

dx/dy = [(2-4y)- y(-4) ]/y^2
= [2-4y+4y]/y^2 = 2/y^2
d^2x/dy^2 =-4y/y^4
= -4/y^3
when y = 2
d^2x/dy^2 = -4/8 = -1/2