If x2 + 5 = 2x - 4 cos (a + bx) where a, b ϵ (0, 5) is satisfied for alteast one real x, then the minimum value of a + bx is
π
x2 + 5 = 2x - 4 cos (a + bx)
x2 - 2x + 1 + 4 = - 4 cos (a + bx)
(x−1)2 + 4 (1 + cos (a + bx)) = 0
∴ x - 1 = 0, cos (a + bx) = -1
∴ minimum of a + bx = π