\sum_{k=100}^{201} \binom{201}{k+1} \binom{k+1}{101}
Is what I got after using the hockey stick identity. I then carried out both combinations but was not sure how to rearrange them after?
I'm quite stuck with how to approahc this type of question.
Σ(k=100 to 201) Σ(j=100 to k) (201 over k+1)(j over 100)
Sorr for the set up, it is tricky to type. The brackets indicated a combination.
I was wondering if someone could help me with a proof.
If ab<0 (can we assume that either a or b is negative then?) and d(gcd of a and b)│c, there there is at least one solution of ax+by=c with x and y positive.