3²/2x4+5²/4x6+...+99²/98x100

=9/8+25/24+...+9801/9800

=1+1/8+1+1/24+...+1+1/9800

=1+1+...+1+1/2.4+1/4.6+...+1/98.100

= 49 + A

với A=1/2.4+1/4.6+...+1/98.100

=1/4(1/1.2+1/2.3+...+1/49.50)

=1/4(1-1/2+1/2-1/3+...+1/49-1/50)

=1/4(1-1/50)

=1/4.49/50

=49/200

ta có:3²/2x4+5²/4x6+...+99²/98x100= 49+A= 49+49/200=9849/200

chúc bạn hok tốt

C=1/(2x4)+1/(4x6)+...+1/(18x20)

2C=2/(2x4)+2/(4x6)+...+2/(18x20)

2C=1/2-1/4+1/4-1/6+....-1/20

2C= 1/2- 1/20

2C= 9/20

C= 9/20 x 1/2

C= 9/40

- Quên k auto súc vặc

\(=\dfrac{-7}{2022}\left(\dfrac{503}{3}+\dfrac{508}{3}\right)+\dfrac{7}{3}=\dfrac{-7}{2022}\cdot\dfrac{1011}{3}+\dfrac{7}{3}\)

\(=\dfrac{-7}{6}+\dfrac{7}{3}=\dfrac{-7}{6}+\dfrac{14}{6}=\dfrac{7}{6}\)

co ai ko

cuu voi

`(2/(2xx4)+2/(4xx6)+2/(6xx8)+2/(8xx10))xxy=1/3`

`=>(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10)xxy=1/3`

`=>(1/2-1/10)xxy=1/3`

`=>(5/10-1/10)xxy=1/3`

`=>4/10xxy=1/3`

`=>2/5xxy=1/3`

`=>y=1/3:2/5`

`=>y=1/3xx5/2`

`=>y=5/6`

giúp tui với mai tui kt rùi

\(\dfrac{3}{2}\)x\(\dfrac{4}{3}\)x\(\dfrac{5}{4}\)x...x\(\dfrac{2022}{2023}\)

⇒

⇒\(\dfrac{2022}{2}\)=1011

2022/2=1011

=1(2+1)+2(3+1)+3(4+1)+...+100(101+1)

=1.2+1+2.3+2+3.4+3+...+100.101+100

=(1.2+2.3+3.4+..+100.101)+(1+2+3+...+100)

=333300+5000

=338300