PointF vec1 = new PointF(a*(point[1].x-point[0].x), a*(point[1].y-point[0].y));
PointF vec2 = new PointF(b*(point[2].x-point[0].x), b*(point[2].y-point[0].y));

return new PointF(point[0].x+vec1.x+vec2.x, point[0].y+vec1.y+vec2.y);