`b) B = (3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)`

`=> 2B = (3-1)(3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)`

`=> 2B = (3^2-1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)`

`=> 2B = (3^4-1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)`

`=> 2B = (3^8-1)(3^8+1)(3^16+1)(3^32+1)`

`=> 2B = (3^16-1)(3^16+1)(3^32+1)`

`=> 2B = (3^32-1)(3^32+1)`

`=> 2B = 3^64-1`

`=> B = (3^64-1)/2`

`h) H = (a+b)^3 + (b+c)^3 + (c+a)^3 - 3(a+b)(b+c)(c+a)`

Đặt `x = a+b, y = b+c, z = c+a`

`H = x^3 + y^3 + z^3 - 3xyz`

Ta có:

`x+y+z = (a+b)+(b+c)+(c+a) = 2(a+b+c)`

`x^2+y^2+z^2-xy-yz-zx = a^2+b^2+c^2-ab-bc-ac`

`=> H = 2(a+b+c)(a^2+b^2+c^2-ab-bc-ac)`

Mà `a^3+b^3+c^3-3abc = (a+b+c)(a^2+b^2+c^2-ab-bc-ac)`

`=> H = 2(a^3+b^3+c^3-3abc)`