What is the coefficient of `x^2` when `(1+x)(1+2x)...(1+2^nx)` is expanded?

•  This is the problem that I picked up from book : 101 Solved Problem in Algebra from The USA IMO with the 32th problem. 

•  This is the polynomial problem which you need to know about expanding method. I will translate for you in Khmer Language.

        ក្នុងនាមជាជនជាតិខ្មែរម្នាក់ ខ្ញុំនឹងចែករំលែកនូវអ្វីដែលអាចធ្វើទៅរួចជាមួយការអប់រំ បទពិសោធន៍ដែលបានឆ្លងកាត់ ។

• Click Read More To Watch Solution and Downlo

•  You can watch solution below which is solved by Thin Sokkean 
• Click Here to Download PDF: USA 32