2) Tính A=2/1.3+2/3.5+2/5.7+…..+2/2019+2021 Nhanh lên nhé 02/11/2021 Bởi Everleigh 2) Tính A=2/1.3+2/3.5+2/5.7+…..+2/2019+2021 Nhanh lên nhé
$A=\dfrac2{1.3}+ \dfrac2{3.5}+ \dfrac2{5.7}+…+ \dfrac2{2019.2021}$ $= 1-\dfrac1{3}+\dfrac1{3}-\dfrac1{5}+\dfrac1{5}-\dfrac1{7}+…+\dfrac1{2019}-\dfrac1{2021}$ $= 1-\dfrac1{2021}$ $= \dfrac{2020}{2021}$ Bình luận
Đáp án: A=2/1.3+2/3.5+2/5.7+…..+2/2019+2021 A= 1 – 1/3 + 1/3 – 1/5 +…+1/2019 – 1/2021 A= 1 + (1/3 – 1/3) + (1/5 – 1/5) + …. + (1/2019 – 1/2019) – 1/2021 A = 1 – 1/2021A = (2021-1)/2021 A = 2020/2021 #NOCOPY Bình luận
$A=\dfrac2{1.3}+ \dfrac2{3.5}+ \dfrac2{5.7}+…+ \dfrac2{2019.2021}$
$= 1-\dfrac1{3}+\dfrac1{3}-\dfrac1{5}+\dfrac1{5}-\dfrac1{7}+…+\dfrac1{2019}-\dfrac1{2021}$
$= 1-\dfrac1{2021}$
$= \dfrac{2020}{2021}$
Đáp án:
A=2/1.3+2/3.5+2/5.7+…..+2/2019+2021
A= 1 – 1/3 + 1/3 – 1/5 +…+1/2019 – 1/2021
A= 1 + (1/3 – 1/3) + (1/5 – 1/5) + …. + (1/2019 – 1/2019) – 1/2021
A = 1 – 1/2021
A = (2021-1)/2021
A = 2020/2021
#NOCOPY