How many distinct lines pass through the point and intersect the parabola at two lattice points? (A lattice point is a point whose coordinates are integers.)
Solution
1. Let the line intersect the parabola at two lattice points and . The line also passes through the point .
2. The equation of the line passing through and can be written as:
where is the slope of the line.
3. Since the line also passes through , we have:
4. The slope can be determined by the two points and :
Therefore, the equation of the line becomes:
5. Substituting into the line equation when :
Simplifying, we get:
6. We need to find pairs such that and both and are integers.
7. The number 2016 can be factored into its prime factors:
The total number of divisors of 2016 is:
8. Since , for each positive divisor of 2016, there is a corresponding negative divisor . Thus, there are 36 pairs such that .
9. Each pair corresponds to a distinct line passing through and intersecting the parabola at two lattice points.
Therefore, the number of distinct lines is .