Ta có :\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)  ( ghi sai đề nha ! ) 

= \(\frac{32}{32}-\frac{1}{32}\)=\(\frac{31}{32}\)

đăng kí kênh của v-i-s nha !

=10000000000000000

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

\(=\frac{275}{7}\)

\(3\frac{1}{5}+\frac{3}{4}-\frac{1}{2}:\frac{2}{7}=\frac{16}{5}+\frac{3}{4}-\frac{7}{4}=\frac{11}{5}\)

\(3\frac{4}{7}4\frac{2}{5}2\frac{1}{2}=\frac{275}{7}\)

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

\(=3\frac{1}{5}+\frac{3}{4}+\frac{7}{4}\)

\(=\frac{11}{5}\)

a) 1+5+11+13+4+9

=(1+5+4)+(11+9)+13

=10         +   20   +13

=             30        +13

=                       43.

ghép những số cộng lại mà tròn chục là được

\(=1\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)

\(=1\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-...+\frac{1}{9}-\frac{1}{10}\right)\)

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

\(=\frac{9}{10}\)

1/2-1/10=2/5

Chúc bạn may mắn@

\(\frac{1}{4}:\frac{x}{9}=\frac{1}{4}\)

\(\frac{x}{9}=\frac{1}{4}:\frac{1}{4}\)

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

\(\Rightarrow x=9\)

Trl:

Bn Vũ Huyền lm đúng r nha!

Hok tốt!!

\(\left(1-\frac{1}{2}\right)x\left(1-\frac{1}{3}\right)x\left(1-\frac{1}{4}\right)x\left(1-\frac{1}{5}\right)x\left(1-\frac{1}{6}\right)\)

\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}.\frac{5}{6}\)

\(=\frac{1.2.3.4.5}{2.3.4.5.6}=\frac{1}{6}\)

Phạm Tuấn Đạt làm đúng rồi đó

Mình cũng làm theo bạn ấy

\(=\frac{4}{3}x\frac{9}{8}x\frac{16}{15}x\frac{25}{24}x...x\frac{100}{99}\)

\(=\frac{2x2x3x3x4x4x5x5x6x6x7x7x8x8x9x9x10x10}{1x3x2x4x3x5x4x6x5x7x6x8x7x9x8x10x9x11}=\frac{2x10}{11}=\frac{20}{11}\)

Lưu Hạ Băng

Ta có : \(1\frac{1}{3}x1\frac{1}{8}x1\frac{1}{15}x1\frac{1}{24}x...x1\frac{1}{99}\)

    \(=\frac{4}{3}x\frac{9}{8}x\frac{16}{15}x\frac{25}{24}x...x\frac{100}{99}\)

    \(=\frac{2x2}{1x3}x\frac{3x3}{2x4}x\frac{4x4}{3x5}x\frac{5x5}{4x6}x...x\frac{10x10}{9x11}\)     

    \(=\frac{2x2x3x3x4x4x5x5x...x10x10}{1x3x2x4x3x5x4x6x...x9x11}\)

    \(=\frac{\left(2x3x4x5x...x10\right)x\left(2x3x4x5x...x10\right)}{\left(1x2x3x4x...x9\right)x\left(3x4x5x6x...x11\right)}\)

    \(=\frac{10x2}{1x11}\)

    \(=\frac{20}{11}\)

Chúc bn học tốt !!!

                    Kb vs mk heg =)) ^^