Đáp án A
( 1 + x ) 2017 = C 2017 0 + C 2017 1 x + ... + C 2017 2017 x 2017
Lấy đạo hàm hai vế ta được:
2017 1 + x 2016 = C 2017 1 + 2 C 2017 2 x + ... + 2017 C 2017 2017 x 2016 ( 1 + x ) 2016 = 1 2017 ( C 2017 1 + 2 C 2017 2 x + ... + 2017 C 2017 2017 x 2016 ) x = 3 ⇒ 4 2016 = 1 + 1 2017 ( 2.3 C 2017 2 + ... + 2017.3 2016 C 2017 2017 ) ⇒ 1 2017 ( 2.3 C 2017 2 + ... + 2017.3 2016 C 2017 2017 ) = 4 2016 − 1