Tính tổng
S
=
1
+
2.2
+
3.2
2
+
4.2
3
+
...
+
2018.2
2017
.
A.
S
=
2017.2
2018
+
1.
B.
S
=
2017.2
2018
.
C.
S
=
2018.2
2018
+
1.
D.
S
=
2019.2
2018
+
1.
...
Đọc tiếp
Tính tổng S = 1 + 2.2 + 3.2 2 + 4.2 3 + ... + 2018.2 2017 .
A. S = 2017.2 2018 + 1.
B. S = 2017.2 2018 .
C. S = 2018.2 2018 + 1.
D. S = 2019.2 2018 + 1.
Đáp án A
y = x + x 2 + x 3 + ... + x 2018 = x 1 − x 2018 1 − x y ' = 1 + 2 x + 3 x 2 + ... + 2018 x 2017 = 2018 x 2019 − 2019 x 2018 + 1 ( 1 − x ) 2 y ' ( 2 ) = 1 + 2.2 + 3.2 2 + ... + 2018.2 2017 = 2017.2 2018 + 1