這種題目應該都是
k^2 / 1.3225^k > (k + 1)^2 / 1.3225^(k + 1)
k^2 / 1.3225^k > (k - 1)^2 / 1.3225^(k - 1)

數學一第 9 題

(a_1 + a_2 + ... + a_n)(a_1^3 + a_2^3 + ... + a_n^3) ≧ (a_1^2 + a_2^2 + ... + a_n^2)^2
等號成立於 a_1 = a_2 = ... = a_n

a_1 = 40/n，a_1^2 = 100/n，解 n