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

\(\frac{9}{4}-y.\frac{5}{6}=\frac{3}{6}+\frac{4}{6}\)

\(\frac{9}{4}-y.\frac{5}{6}=\frac{7}{6}\)

           \(y.\frac{5}{6}=\frac{9}{4}-\frac{7}{6}\)

           \(y.\frac{5}{6}=\frac{27}{12}-\frac{14}{12}\)

           \(y.\frac{5}{6}=\frac{13}{12}\)

           \(y=\frac{13}{12}:\frac{5}{6}\)

           \(y=\frac{13}{12}.\frac{6}{5}\)

           \(y=\frac{13}{2}.\frac{1}{5}\)

           \(y=\frac{13}{10}\)

9/4;4/5;5/7;7/12;5/12

Tính

\(D=\frac{5}{1.6}+\frac{5}{6.11}+\frac{5}{11.16}+...+\frac{5}{86.91}\)

\(=1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+...+\frac{1}{86}-\frac{1}{91}\)

\(=1-\frac{1}{91}=\frac{91}{91}-\frac{1}{91}=\frac{90}{91}\)

Vậy \(D=\frac{90}{91}.\)

\(D=\frac{5}{1.6}+\frac{5}{6.11}+\frac{5}{11.16}+...+\frac{5}{86.91}\)

\(=1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+....+\frac{1}{86}-\frac{1}{91}\)

\(=1-\frac{1}{91}\)

\(=\frac{91}{91}-\frac{1}{91}\)

\(=\frac{90}{91}\)

Vậy \(D=\frac{90}{91}\)

Chúc bạn học tốt !

4/3x6+4/6x9+4/9x12+4/12x15=8+6+16/3+5

                                            =73/3

tick nha

\(\frac{4}{3}\times6+\frac{4}{6}\times12+\frac{4}{12}\times15\)

\(=\frac{4}{3}\times6+\frac{2}{3}\times6\times2+\frac{1}{3}\times15\)

\(=\left(\frac{4}{3}+\frac{2}{3}\right)\times6\times2+5\)

\(=2\times6\times2+5\)

\(=24+5\)

\(=29\)

Gọi tổng trên là A

A = 3/4(3/3.6 + 3/6.9 + 3/9.12 + 3/12.15)

A = 3/4( 1 - 1/6 + 1/6 - 1/9 + 1/9 - 1/12 + 1/12 - 1/15)

A = 3/4(1 - 1/15)

A = 3/4 . 14/15

A = 7/10

Nếu có gì sai thì nói với mk nha

bằng hỗn số 24/1/3

bn tự đổi ra nha

4/3x6 + 4/6x9 + 4/9x12 + 4/12x15

=4/3x(1/3-1/6+1/6 -1/9 + 1/9 - 1/12 +1/12 - 1/15)

=4/3 x (1/3-1/15)

=4/3 x 4/15 

=16/45

chúc bạn làm bài tốt nhé

khó quá mk giải miết mà không ra

khó vãi

D

b

D