Ta có : $3(2^2+1)(2^4+1)(2^8+1)(2^{16}+1)(2^{32}+1)$
$=(2^2-1)(2^2+1)(2^4+1)(2^8+1)(2^{16}+1)(2^{32}+1)$
$=(2^4-1)(2^4+1)(2^8+1)(2^{16}+1)(2^{32}+1)$
$=(2^8-1)(2^8+1)(2^{16}+1)(2^{32}+1)$
$=(2^{16}-1)(2^{16}+1)(2^{32}+1)$
$=(2^{32}-1)(2^{32}+1)$
$=2^{64}-1$
3.(22+1)(24+1)(28+1)(216+1)(232+1)
= (22-1)(22+1)(24+1)(28+1)(216+1)(232+1)
= (24-1)(24+1)(28+1)(216+1)(232+1)
= (28-1)(28+1)(216+1)(232+1)
= (216-1)(216+1)(232+1)
= (232-1)(232+1)
= 264 - 1
Gợi ý: Áp dụng hằng đẳng thức số 3 trong 7 hằng đẳng thức đáng nhớ