Question

Let {x} and [x] denote the fractional part of x and the greatest integer ≤ x respectively of a real number x. If ∫({x} dx, [x] dx) for x ∈ [0,n] and 10(n² – n), (n ∈ N, n > 1) are three consecutive terms of a G.P., then n is equal to____

Answer 1

= (n - 1)/4 = 5 

n = 21