Find the general solution of the differential equation (1 + tan y)(dx – dy) + 2xdy = 0.

Find the points on the curve y = x³ at which the slope of the tangent is equal to y-coordinate of the point.
If the radius of sphere is measured as 9 cm with an error of 0.03 cm, then find the approximate error in calculating its surface area.
Find the particular solution of the following differential equation :
y = 0 when x = 0.