Question
Question: If (1 + x) (1 + x<sup>2</sup>) (1 + x<sup>4</sup>)……(1 + x<sup>128</sup>) =  (1 + x2) (1 + x4)……(1 + x128) = then n is –
A
225
B
255
C
60
D
127
Answer
255
Explanation
Solution
(1 + x) (1 + x2) (1 + x3)…..(1 + x128)
= 1 + x + x2 + ….+ xn
̃ (1 – x) {(1 + x) (1 + x2) (1 + x3)}……(1 + x128)
̃ (1 – x256) = (1 – xn + 1)
̃ n + 1 = 256
n = 225.