Let L ≡ 2x + 3y − 1 = 0,La' ≡ + 2y − 3 = 0 and L" 5x − 6y − 1 = 0. Vertices are A (5/4, 7/8), B (1/3, 1/9) and C (−7, 5). See Fig.
1 . For the side BC (L = 0), the points A(5/4, 7/8) and (α, α2) must be on the same side
Therefore,
α < -1 or α > 1/3 ...(1)
2. For the side CA (L' = 0), the points B(1/3, 1/9) and (α, α2) are on the same side. Therefore
3. For the side AB (L" = 0), the points C and (α, α2) are on the same side. Therefore
From Eqs. (1) - (3) ,α ∈ (-3/2, -1) ∪ (1/2, 1).