Từ đầu bài =) (101+103+105+107+109)-(102+104+106+108)

                 =      [(101+109)+(103+107)+105]-[(102+108)+(104+106)]

                  =      210+210+105-210-210

                  =   0+105

                   =         105

101-102-(-103)-104-(-105)-106-(-107)-108-(-109)

= 101-102+103-104+105-106+107-108+109

= (101+109) - (102 +108) +(103+107)-(104+106) +105

= 210-210+210-210 +105

=105

Số số hạng của dãy là :  ( số )

 Có  ( cặp )

`1-5+9-13+...+393-397`

`=(1-5)+(9-13)+...+(393-397)` (197 cặp)

`=(-4)+(-4)+...+(-4)` 

`=(-4) xx 197`

`=-788`

\(\left(9^{98}\cdot80+9^{98}\right):9^{100}\)   

\(=\frac{9^{98}\cdot80+9^{98}}{9^{100}}\)   

\(=\frac{9^{98}\cdot\left(80+1\right)}{9^{100}}\)   

\(=\frac{9^{98}\cdot81}{100}\)  

\(=\frac{9^{98}\cdot9^2}{9^{100}}\)   

\(=\frac{9^{100}}{9^{100}}=1\)

đáp án bằng 1

 \(\left(-\frac{3}{4}+\frac{59}{9}\right):\left(-\frac{7}{23}\right)+\left(\frac{5}{9}-\frac{1}{4}\right):\frac{7}{23}\)

= \(\left(-\frac{3}{4}+\frac{59}{9}\right).\left(-\frac{23}{7}\right)+\left(\frac{5}{9}-\frac{1}{4}\right).\left(\frac{23}{7}\right)\)

=\(\left(-\frac{23}{7}\right).\left(-\frac{3}{4}+\frac{59}{9}-\frac{5}{9}+\frac{1}{4}\right)\)

=\(\left(-\frac{23}{7}\right).\left(-\frac{2}{4}+\frac{54}{9}\right)=\left(-\frac{23}{7}\right).\left(-\frac{1}{4}+6\right)\)

=\(\left(-\frac{23}{7}\right).\frac{11}{2}=-\frac{253}{14}\)

-5/2×(2/11+9/11)×(-5/7+15/7)

-5/2×1×10/7

-5/2×10/7

25/7

3^10 . 10 + 3^ 11 . 5 / 3^9 . 5^2

= 3^10 . 2 . 5 + 3^10 . 3 . 5 / 3^9 . 5^2

= 3^10 ( 2 . 5 + 3 .5 ) / 3^9 . 5^2 

= 3^10 [ 5 ( 2 + 3 ) ] / 3^9 . 5^2

= 3^10 ( 5 . 5 ) / 3^9 . 5^2

= 3^10 . 5^2 / 3^9 . 5^2

= 3^10 / 3^9

= 3^9 . 3 / 3^9

= 3

(2³.9⁴+9³.45):(9².10-9²)

= ( 8. 9⁴+9³.9.5):(81.10-81)

= (8.9⁴+9⁴.5):(810-81)

=[9⁴.(8+5)]:729

=[9⁴.13]:729

=6561.13:729

=6561:729.13

=9.13

=117

Mk nhanh nhat day

(2³.9⁴+9³.45):(9².10-9²)

=(2³.9⁴+5.9⁴):(81.10-81)

=[9⁴.(8+5)]:(810-81)

=(6561.13):729

=85296:729

=117

`8 2/7-(3 4/9+4 2/7)`

`=8+2/7-(3+4/9+4+2/7)`

`=8+2/7-7-2/7-4/9`

`=1-4/9`

`=5/9`

8 2/7-(3 4/9+4 2/7)

=58/7-31/9-30/7

=(58/7-30/7)-31/9

=4-31/9

=5/9