Sửa đề: \(A=\frac12+\frac56+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}+\frac{109}{110}\)

\(=1-\frac12+1-\frac16+1-\frac{1}{12}+1-\frac{1}{20}+\cdots+1-\frac{1}{110}\)

\(=10-\left(\frac12+\frac16+\frac{1}{12}+\cdots+\frac{1}{110}\right)\)

\(=10-\left(1-\frac12+\frac12-\frac13+\frac13-\frac14+\cdots+\frac{1}{10}-\frac{1}{11}\right)\)

\(=10-\left(1-\frac{1}{11}\right)=10-\frac{10}{11}=\frac{110}{11}-\frac{10}{11}=\frac{100}{11}\)

Đm

= 82. ( -71 - 29 ) + 1

= 82. ( -100 ) +1

= -8200 + 1 = -8199

\(\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+.....+\frac{71}{72}+\frac{89}{90}\)

\(=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+....+\left(1-\frac{1}{72}\right)+\left(1-\frac{1}{90}\right)\)

\(=\left(1+1+1+....+1\right)-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+....+\frac{1}{90}\right)\)

\(=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{9.10}\right)\)

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

\(=9-\left(1-\frac{1}{10}\right)=9-\frac{9}{10}=\frac{81}{10}\)

a: \(\left[\left(-59\right)+71\right]-\left[\left(-83\right)-\left(-95\right)\right]\)

\(=\left[71-59\right]-\left[-83+95\right]\)
=12-12

=0

b: \(\left(435-167-89\right)-\left(435-89\right)\)

\(=435-167-89-435+89\)

\(=\left(435-435\right)+\left(89-89\right)-167\)

=0+0-167

=-167

c: \(\left(-624\right)-\left[\left(376+245\right)-45\right]\)

\(=\left(-624\right)-\left[376+245-45\right]\)

\(=\left(-624\right)-376-200\)

=-1000-200

=-1200

Vì 32/71 < 1 mà 89/88 > 1 => 32/72 < 89/88

24

tick mk nha,mk tick lại

`53/89 xx11/61 xx 71/37 xx 0`

`=53/89 xx11/61 xx 0`

`=53/89 xx0`

`=0`

73/79>71/82 dung do tk cho to nha

73/79>71/82

86-84+82-80+...+8-6+4-2

=2+2+2+...+2+2+2 (có tất cả 21 số 2)

=2.21

=42

77-75+73-71+...+7-5+3-1

= 2 + 2 + ... + 2 ( có 38 số 2)

= 2 . 38

= 76

 tick đúng cho mình nhé !