\(B=\left(\dfrac{5}{2019}+\dfrac{4}{2020}-\dfrac{3}{2021}\right)\cdot\dfrac{3-2-1}{6}=0\)
\(B=\left(\dfrac{5}{2019}+\dfrac{4}{2020}-\dfrac{3}{2021}\right)\cdot\dfrac{3-2-1}{6}=0\)
tính bằng cách thuận tiện
1-2 + 3-4 + 5-6 + 7-8 + ....... + 2019-2020 + 2021
Tính hợp lý:
a) A=\(2021^2\)-2020.(2021+1)
b) B=1+2-3-4+5+6-7-8+9+10-...+2018-2019-2020+2021
c) C=\(\dfrac{5.4^{15}.9^9-4.3^{20}.8^9}{5.2^9.6^{19}-7.2^{29}.27^6}\)
Tính hợp lí (nếu có thể):
A= -1-2+3+4-5-6+7+8-9-10+...+2019+2020-2021-2022+2023
tính nhanh: (1+3+5+7+...+2019+2021)-(2+4+6+8+...+2020)
Tính S= 1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + 9 + 10 - ... + 2018 - 2019 - 2020 + 2021
Tính S= 1+2-3-4+5+6-7-8+9+10- .......+2018-2019-2020+2021
tính :
A= 1+2-3-4+5+6-7-8+9+...+2018-2019-2020+2021-2022
Tính: S = 1+2-3-4+5+6-7-8+9+10+ ..... + 2018-2019-2020+2021
tính s = 1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + 9 + 10 -... + 2018 - 2019 - 2020 + 2021