k mình nha mấy bạn mình bị âm quá trời quá đất lun nè hu..............huhu

Đăng bài gì mà dễ thế! tớ lớp 5 giải còn được đấy! Ai thấy tớ đúng thì tk nha

k cho mik mk h lại liên hệ qua tin nhan

\(A=\frac{15}{90.94}+\frac{15}{94.98}+...+\frac{15}{146.150}\)

\(A=15\left(\frac{1}{90.94}+\frac{1}{94.98}+...+\frac{1}{146.150}\right)\)

\(A=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+...+\frac{1}{146}-\frac{1}{150}\right)\)

\(A=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{150}\right)\)

\(A=\frac{15}{4}.\frac{1}{225}\)

\(A=\frac{1}{60}\)

\(\frac{15}{90.94}+\frac{15}{94.98}+\frac{15}{98.102}+...+\frac{15}{146.150}\)

\(=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+\frac{1}{98}-\frac{1}{102}+...+\frac{1}{146}-\frac{1}{150}\right)\)

\(=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{150}\right)\)

\(=\frac{15}{4}.\frac{1}{225}\)

\(=\frac{1}{60}\)

\(\frac{15}{90\cdot94}+\frac{15}{94\cdot98}+\frac{15}{98\cdot102}+...+\frac{15}{146\cdot150}\)

\(=\frac{15}{4}\cdot\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+\frac{1}{98}-\frac{1}{102}+...+\frac{1}{146}-\frac{1}{150}\right)\)

\(=\frac{15}{4}\cdot\left(\frac{1}{90}-\frac{1}{150}\right)\)

\(=\frac{15}{4}\cdot\frac{1}{225}=\frac{1}{60}\)

a)(ghi lại đề)

=\(\frac{15}{4}\)x( \(\frac{4}{90}\)x 94+\(\frac{4}{94}\) x 98+...+\(\frac{4}{146}\)x150)

=15/4 x[(1/90 -1/94)+(1/94-1/98)+...+1/146-1/150)]

=15/4x (1/90-1/150)

=15/4 x 2/2450

=1/60

(Lúc đầu siêng nên ghi dài còn lúc sau lười r , k hỉu thj hỏi)

Ta có: \(A=\frac{1}{15.18}+\frac{1}{18.21}+...+\frac{1}{87.90}\)

                \(=\frac{1}{3}(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+...+\frac{1}{87}-\frac{1}{90})\)

                \(=\frac{1}{3}(\frac{1}{15}-\frac{1}{90})\)

                \(=\frac{1}{3}(\frac{6}{90}-\frac{1}{90})\)

                \(=\frac{1}{3}.\frac{5}{90}\)

                \(=\frac{1}{54}\)

Ta có: 1= \(\frac{54}{54}\)

Suy ra A < 1 (đpcm)

3A=3*(1/15*18+1/18*21+...+1/87*90)

3A=3/15*18+3/18*21+...+3/87*90

3A=1/15-1/18+1/18-1/21+...+1/87-1/90

3A=1/15-1/90

3A=1/18

A=1/18 chia3

A=1/54

vì 1/54<1 nên A<1

3A là gì vậy

bạn xem lai đề phần a đi mik giúp cho

Ta có : 

\(H=\frac{15}{90.94}+\frac{15}{94.98}+\frac{15}{98.102}+...+\frac{15}{146.150}\)

\(H=\frac{15}{4}\left(\frac{4}{90.94}+\frac{4}{94.98}+\frac{4}{98.102}+...+\frac{4}{146.150}\right)\)

\(H=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+\frac{1}{98}-\frac{1}{102}+...+\frac{1}{146}-\frac{1}{150}\right)\)

\(H=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{150}\right)\)

\(H=\frac{15}{4}.\frac{1}{225}\)

\(H=\frac{1}{60}\)

Vậy \(H=\frac{1}{60}\)

Chúc bạn học tốt ~ 

\(H=\frac{15}{90\cdot94}+\frac{15}{94\cdot98}+\frac{15}{98\cdot102}+...+\frac{15}{146\cdot150}\)

\(H=15\left(\frac{1}{90\cdot94}+\frac{1}{94\cdot98}+\frac{1}{98\cdot102}+...+\frac{1}{146\cdot150}\right)\)

\(H=15\left[\frac{1}{4}\left(\frac{4}{90\cdot94}+\frac{4}{94\cdot98}+\frac{4}{98\cdot102}+...+\frac{4}{146\cdot150}\right)\right]\)

\(H=15\left[\frac{1}{4}\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+\frac{1}{98}-\frac{1}{102}+...+\frac{1}{146}-\frac{1}{150}\right)\right]\)

\(H=15\left[\frac{1}{4}\left(\frac{1}{90}-\frac{1}{150}\right)\right]\)

\(H=15\left[\frac{1}{4}\cdot\frac{1}{225}\right]\)

\(H=15\cdot\frac{1}{900}\)

\(H=\frac{1}{60}\)

H = 15/90.94 + 15/94.98 + 15/98.102 + ... + 15/146.150

H = 15(1/90.94 + 1/94.98 + 1/98.102 + ... + 1/146.150)

H = 15/4 (4/90.94 + 4/94.98 + 4/98.102 + ... +4/146.150)

H = 15/4 ( 1/90 - 1/94 + 1/94 - 1/98 + 1/98 - 1/102 + ... + 1/146 - 1/150)

H = 15/4 (1/90 - 1/150)

H = 15/4 (5/450 - 3/450)

H = 15/4 . 1/225

H = 1/60

\(A=\frac{21}{31}+\frac{-16}{7}+\frac{44}{53}+\frac{10}{21}+\frac{9}{53} \)

\(A=\left(\frac{16}{7}+\frac{10}{21}\right)+\left(\frac{44}{53}+\frac{9}{53}\right)+\frac{21}{31}\)

\(A=\frac{58}{21}+1+\frac{21}{31}\)

\(A=\frac{100}{21}\)

\(B=6\left(\frac{1}{15.18}+\frac{1}{18.21}+...+\frac{1}{87.90}\right)\)

\(B=6\left(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+...+\frac{1}{87}-\frac{1}{90}\right)\)

\(B=6\left(\frac{1}{15}-\frac{1}{90}\right)\)

\(B=6.\frac{1}{18}\)

\(B=\frac{1}{3}\)

\(E=\frac{1}{25\cdot27}+\frac{1}{27\cdot29}+...+\frac{1}{73\cdot75}\)

\(E=\frac{1}{2}\left(\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+...+\frac{1}{73}-\frac{1}{75}\right)\)

\(\Rightarrow E=\frac{1}{2}\left(\frac{1}{25}-\frac{1}{75}\right)=\frac{1}{2}\cdot\frac{2}{75}=\frac{1}{75}\)

\(F=\frac{15}{90\cdot94}+\frac{15}{94\cdot98}+...+\frac{15}{146\cdot150}\)

\(F=\frac{15}{4}\cdot\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+...+\frac{1}{146}-\frac{1}{150}\right)\)

\(\Rightarrow F=\frac{15}{4}\cdot\left(\frac{1}{90}-\frac{1}{150}\right)=\frac{15}{4}\cdot\frac{1}{225}=\frac{1}{60}\)

\(G=\frac{10}{56}+\frac{10}{140}+\frac{10}{260}+...+\frac{10}{1400}\)

\(G=\frac{5}{28}+\frac{5}{70}+\frac{5}{130}+...+\frac{5}{700}\)

\(G=\frac{5}{4\cdot7}+\frac{5}{7\cdot10}+\frac{5}{10\cdot13}+...+\frac{5}{25\cdot28}\)

\(G=\frac{5}{3}\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+...+\frac{1}{25}-\frac{1}{28}\right)\)

\(\Rightarrow G=\frac{5}{3}\left(\frac{1}{4}-\frac{1}{28}\right)=\frac{5}{3}\cdot\frac{3}{14}=\frac{5}{14}\)

sao nhiều vậy bạn 

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