Consider the hyperbola a2x2−b2y2=1 having one of its focus at P(−3,0). If the latus rectum through its other focus subtends a right angle at P and a2b2=α2−β, α,β∈N, then α+β is
Answer: 1944
Solution
The focus at (−3,0) gives ae=3, and the latus rectum through the other focus (3,0) has endpoints (3,±ab2). For these endpoints to subtend a right angle at (−3,0) each makes 45∘ with the axis, so 6b2/a=1, giving b2=6a. Substituting into a2e2=a2+b2 gives 9=a2+6a, so a=3(2−1). Then a2b2=6a3=6(1352−189)=8102−1134, so α=810 and β=1134, and α+β=1944.