Find dy/dx by implicit differentiation.
x^4 + x^3y + 4y^2 = 7
x cos y + y cos x = 1
4x^3 + 3x^2y + x^3 y' + 8y y' = 0
y'(x^3 + 8y) = -x^2 (4x+3y)
y' = -x^2 (4x+3y) / (x^3 + 8y)
do the other likewise and simplify
x^4 + x^3y + 4y^2 = 7
x cos y + y cos x = 1
y'(x^3 + 8y) = -x^2 (4x+3y)
y' = -x^2 (4x+3y) / (x^3 + 8y)
do the other likewise and simplify