\(A=\dfrac{2}{1\cdot3}+\dfrac{2}{3\cdot5}+\dfrac{2}{5\cdot7}+...+\dfrac{2}{2021\cdot2023}\)

\(A=\dfrac{1}{1}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{2021}-\dfrac{1}{2023}\)

\(A=\dfrac{1}{1}-\dfrac{1}{2023}\\ A=\dfrac{2023}{2023}-\dfrac{1}{2023}\\ A=\dfrac{2022}{2023}\)

$A=\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{97.99}$

$A=\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}$

$A=\frac{1}{1}-\frac{1}{99}$

$A=\frac{98}{99}$

=

21​−51​+51​−71​+....+951​−981​

=12−198=21​−981​tự làm tiếp nha ( giống câu a)

The children went jogging with their parents at the zoo.

The children went jogging with their parents at the zoo

The children went jogging with their parents at the zoo

ket qua la 5435 ban nha

tượng hình

tượng hình

tượng hình

42 . 48 - 24 . 34

= 24 . 84 - 24 . 34

= 24 . (84 - 34)

= 24 . 50

= 1200

42.48-24.34 = 42.48-48.17 = 48(42 - 17) = 48.100:4 = 1200

18,14

cái này có gì khó đâu

X x ab = ab0ab

=> X x ab= ab x 1000 + ab

=> X x ab = ab x 1001

=> X = 1001

đề:)?