a)\(\frac{4}{3.7}+\frac{4}{7.11}+...+\frac{4}{23.27}=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{23}-\frac{1}{27}=\frac{1}{3}-\frac{1}{27}=\frac{8}{27}\)

b)\(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{6.7}=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{6}-\frac{1}{7}=\frac{1}{2}-\frac{1}{7}=\frac{5}{14}\)

c)\(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{11.13}+\frac{2}{1.2}+\frac{2}{2.3}+...+\frac{2}{9.10}=\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{11}-\frac{1}{13}\right)+2\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)

\(=\frac{1}{3}-\frac{1}{13}+2\left(1-\frac{1}{10}\right)=\frac{10}{39}+\frac{9}{5}=\frac{401}{195}\)

hơi khó anh mai ơi !

hơi bị khó... chờ mình ghi lại để hỏi cô!!!

dấu này"/" là chia hay phần

A = ( 4/4 + 2/3 ) - ( 51/3 - 6/5 ) - ( 6 - 7/4 + 3/2 )

Sau đó quy đồng rồi trừ cả là đc 

B tương tự 

C=13/15 

D cx thế . Bạn tự vận dụng đi . Xl vì ko giải đc . Mik đang gấp

Cbhjjkmngh

a: =-5/11-6/11+1=-11/11+1=0

b: =-13/17-13/21-4/17=-1-13/21=-34/21

b: \(=-\dfrac{5}{12}\cdot\dfrac{9}{20}\cdot\dfrac{7}{17}=\dfrac{-21}{272}\)

d: \(=\dfrac{13}{17}\left(-\dfrac{4}{5}-\dfrac{3}{4}\right)=\dfrac{13}{17}\cdot\dfrac{-31}{20}=\dfrac{-403}{340}\)

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G=14⋅7+14⋅9+15⋅11+16⋅11+16⋅13+17⋅13cap G equals one-fourth center dot 7 plus one-fourth center dot 9 plus one-fifth center dot 11 plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13   Giải 1 Thực hiện phép nhân G=14⋅7+14⋅9+15⋅11+16⋅11+16⋅13+17⋅13cap G equals one-fourth center dot 7 plus one-fourth center dot 9 plus one-fifth center dot 11 plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13     G=74+14⋅9+15⋅11+16⋅11+16⋅13+17⋅13cap G equals seven-fourths plus one-fourth center dot 9 plus one-fifth center dot 11 plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13 2 Thực hiện phép nhân G=74+14⋅9+15⋅11+16⋅11+16⋅13+17⋅13cap G equals seven-fourths plus one-fourth center dot 9 plus one-fifth center dot 11 plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13     G=74+94+15⋅11+16⋅11+16⋅13+17⋅13cap G equals seven-fourths plus nine-fourths plus one-fifth center dot 11 plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13 3 Thực hiện phép nhân G=74+94+15⋅11+16⋅11+16⋅13+17⋅13cap G equals seven-fourths plus nine-fourths plus one-fifth center dot 11 plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13     G=74+94+115+16⋅11+16⋅13+17⋅13cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13 4 Thực hiện phép nhân G=74+94+115+16⋅11+16⋅13+17⋅13cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus one-sixth center dot 11 plus one-sixth center dot 13 plus one-seventh center dot 13     G=74+94+115+116+16⋅13+17⋅13cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus eleven-sixths plus one-sixth center dot 13 plus one-seventh center dot 13 5 Thực hiện phép nhân G=74+94+115+116+16⋅13+17⋅13cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus eleven-sixths plus one-sixth center dot 13 plus one-seventh center dot 13     G=74+94+115+116+136+17⋅13cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus eleven-sixths plus thirteen-sixths plus one-seventh center dot 13 6 Thực hiện phép nhân G=74+94+115+116+136+17⋅13cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus eleven-sixths plus thirteen-sixths plus one-seventh center dot 13     G=74+94+115+116+136+137cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus eleven-sixths plus thirteen-sixths plus thirteen-sevenths 7 Thực hiện phép cộng G=74+94+115+116+136+137cap G equals seven-fourths plus nine-fourths plus eleven-fifths plus eleven-sixths plus thirteen-sixths plus thirteen-sevenths     G=42235cap G equals 422 over 35 end fraction   Ẩn bớt Đáp án G=42235cap G equals 422 over 35 end fraction   Dạng thức khác

Ghi đầy đủ nha

bn có thể ghi rõ ràng đc ko?

a)\(-\dfrac{3}{7}+\dfrac{5}{13}+\dfrac{3}{7}\) 

=\(\left(-\dfrac{3}{7}+\dfrac{3}{7}\right)+\dfrac{5}{13}\) 

=\(0+\dfrac{5}{13}\) 

=\(\dfrac{5}{13}\)

a)\(2-3+5-7+9-11+13-15+17=\left(2+5+9+13+17\right)-\left(3+7+11+15\right)\)

                                                                                               \(=46-36=10\)

b)\(\frac{1}{1.2}+\frac{1}{2.3}+...............+\frac{1}{8.9}=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+.................+\frac{1}{8}-\frac{1}{9}\)

                                                                        \(=\frac{1}{1}-\frac{1}{9}=\frac{9}{9}-\frac{1}{9}=\frac{8}{9}\)

Áp dụng \(\frac{1}{n.\left(n+1\right)}=\frac{1}{n}-\frac{1}{n+1}\)

Chúc bạn học tốt

Đề là tính bằng cách hợp lý đúng ko bạn

a, 2-3+5-7+9-11+13-15+17

= (5+13) - (3+15) + (2+9-11) + (17-7)

= 18 - 18 + 0 +10

= 10

b, \(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\)

\(=1-\frac{1}{9}\)

\(=\frac{8}{9}\)

a: =7+5/11-2-3/7-3-5/11

=2-3/7=11/7

b: =-3/5(5/7+3/7+6/7)

=-3/5*2=-6/5

c: =1/3(4/5+6/5)-4/3

=2/3-4/3=-2/3

d: =5/9(7/13+13-3/13)

=5/9*165/13=275/39