câu 1 a=85

câu 2\(\frac{7}{18}\)

câu 3 \(\frac{1}{18}\)

Câu 1:a=85

Câu 2:x=7/18

Câu 3:x=1/18

giúp với ạ

giải dc nhưng mà hoi lâu

\(\frac{1}{2}+\frac{1}{2}=\frac{1+1}{2}=\frac{2}{2}=1\)

\(\frac{3}{4}+\frac{1}{4}=\frac{3+1}{4}=\frac{4}{4}=1\)

\(\frac{3}{9}+\frac{6}{9}=\frac{3+6}{9}=\frac{9}{9}=1\)

a, 1/2+1/2=1

b, 3/4+1/4=1

c, 3/9+6/9=1

k nha bn, ok

\(\frac{1}{2}+\frac{1}{6}+\frac{1}{9}=\frac{9}{18}+\frac{3}{18}+\frac{2}{18}=\frac{14}{18}=\frac{7}{9}\)

1/2 + 1/6 + 1/9

= ( 1/2 + 1/6 ) + 1/9 

= ( 3/6 + 1/6 ) + 1/9

= 4/6 + 1/9

= 2/3 + 1/9

= 6/9 + 1/9

= 7/9

\(\frac{1}{2}:\frac{3}{2}:\frac{5}{4}:\frac{6}{5}:\frac{7}{6}:\frac{8}{7}\)

\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\)

\(=\frac{1\cdot\left(2\cdot5\cdot6\cdot7\right)}{8\cdot3\cdot\left(2\cdot5\cdot6\cdot7\right)}\)

\(=\frac{1}{24}\)

\(\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\cdot\frac{8}{9}\cdot\frac{9}{10}\)

\(=\frac{1\cdot\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)}{\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)\cdot10}\)

\(=\frac{1}{10}\)

=1-\(\frac{1}{2}\)+1/3-1/4+...+1/8-1/9

=1-1/9

=8/9

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

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

\(\frac{1}{6}+\frac{5}{6}=\frac{6}{6}=1\)

\(\frac{25}{5}+\frac{2}{6}=\frac{150}{30}+\frac{10}{30}=\frac{160}{30}=\frac{32}{6}=\frac{16}{3}\)

\(\frac{12}{5}+\frac{6}{9}=\frac{108}{45}+\frac{30}{45}=\frac{138}{45}\)

\(\frac{11}{6}\)

\(\frac{16}{3}\)

\(\frac{46}{3}\)

Gợi ý: Rút gọn 2 ps, quy đồng rồi so sánh.

1 + 3 + 2 + 3 = 9 nhé

bằng 9 nè

9x1=9

9x2=18

9x3=27

9x4=36

9x5=45

9x6=54

9x7=63

9x8=73

9x9=81

9x10=90

2/5+3/6=2/5+1/2=4/10+5/10=9/10

\(\frac{2}{5}+\frac{3}{6}=\frac{12}{30}+\frac{15}{30}=\frac{27}{30}=\frac{9}{10}\)