a) Find all points (a, b) on the curve C, given by y = x + sin x, so that the tangent lines to C at (a, b) are parallel to the line y = x + 15.
b) Find all points (a, b) on the curve C, given by v = 3x2 + 2, so that the tangent lines to C at (a, b) pass through the point (-1, -7).