3 ×17 + 3 × 25 - 3 × 2 = 3 × (17 + 25 – 2) = 3 × 40 = 120

3x(17+25-2)=3x40=120

dap so la \(\frac{29}{10}\)neu roi ve do thap phan thi bang 2,9

dung roi nha ung ho nha

\(\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}+\frac{36}{60}+\frac{49}{72}+\frac{64}{80}\)

Ta có:\(\frac{4}{20}=\frac{2}{10}\);\(\frac{9}{30}=\frac{3}{10}\);\(\frac{16}{40}=\frac{4}{10}\);\(\frac{25}{50}=\frac{5}{10}\);\(\frac{36}{60}=\frac{6}{10}\);\(\frac{49}{70}=\frac{7}{10}\);\(\frac{64}{80}=\frac{8}{10}\)

Ta có:\(\frac{2}{10}+\frac{3}{10}+\frac{4}{10}+\frac{5}{10}+\frac{6}{10}+\frac{7}{10}+\frac{8}{10}\)=\(\frac{2+3+4+5+6+7+8}{10}\)=\(\frac{36}{10}\)=\(3\frac{3}{5}\)

Chúc bạn học tốt Thảo Nhi

=4 nhé bạn

làm sao dậy

4 nha bạn

Rút gọn tất cả các phân số ta có: 

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

\(=\frac{1+2+3+4+5+6+7+8+9}{10}=\frac{45}{10}=\frac{9}{2}\)

cam on thinh nha thank you so much

\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}+\frac{36}{60}+\frac{49}{70}+\frac{64}{80}+\frac{81}{90}\)

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

=\(\frac{1+2+3+4+5+6+7+8+9}{10}=\frac{45}{10}=4,5\)

Chúc bn học tốt

a) (14 + 38 + 66) - (10 + 4 - 16)

= 14 + 38 + 66 - 10 - 4 + 16

= (14 - 4) + (66 + 38 + 16) - 10

= 10 + 120 - 10

= 120

b) (70 + 20 - 60) - (-30 - 80 + 120)

= 70 + 20 - 60 + 30 + 80 - 120

= (70 + 30) + (20 + 80) - (120 + 60)

= 100 + 100 - 180

= 200 - 180

= 20

a, (14 + 38 + 66) - (10 + 4 - 16)

   = 14 + 38 + 66 - 10 - 4 + 16

= (14 - 4 - 10) + (38 + 66 + 16)

= 0 + 120

= 120 

1/10 + 4/20 + 9/30 + 16/40 + 25/50 + 36/60 + 49/70 + 64/80 + 81/90 
= 1/10 + 2/10 + 3/10 + 4/10 + 5/10 + 6/10 + 7/10 + 8/10 + 9/10 
=(1+2+3+....+9) /10 
=(1+9)x9:2 /10 
=45/10=4,5 

chắc chắn đúng đó  

\(M=\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+...+\frac{81}{90}\)

\(M=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}+...+\frac{9}{10}\)

\(M=\frac{\left(9+1\right)\cdot\left(9-1+1\right):2}{10}\)

\(M=\frac{10\cdot9:2}{10}=4,5\)

tớ làm giống bạn kia

tớ cũng làm như vậy

a; \(\dfrac{1}{4}\) + \(\dfrac{2}{5}\) + \(\dfrac{6}{8}\) + \(\dfrac{9}{15}\) + \(\dfrac{8}{1}\)

= (\(\dfrac{1}{4}\) + \(\dfrac{6}{8}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{9}{15}\)) + \(\dfrac{8}{1}\)

= (\(\dfrac{1}{4}\) + \(\dfrac{3}{4}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{3}{5}\)) + 8

=  1 + 1 + 8

=  2 + 8

= 10

b; \(\dfrac{1}{2}\) + \(\dfrac{2}{4}\) + \(\dfrac{3}{6}\) + \(\dfrac{4}{8}\) + \(\dfrac{5}{10}\) + \(\dfrac{6}{12}\) + \(\dfrac{7}{14}\) + \(\dfrac{8}{16}\) + \(\dfrac{10}{20}\)

=  \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x (\(\dfrac{2}{2}\) + \(\dfrac{3}{3}\) + \(\dfrac{4}{4}\) + \(\dfrac{5}{5}\)+ \(\dfrac{6}{6}+\dfrac{7}{7}+\dfrac{8}{8}\) + \(\dfrac{10}{10}\))

= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x (1 + 1 +1 + 1+ 1+ 1+ 1 +1)

= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x 1 x 8

= \(\dfrac{1}{2}\) + \(\)\(\dfrac{1}{2}\) x 8

= \(\dfrac{1}{2}\) + 4

= \(\dfrac{9}{2}\) 

c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)

= \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)

= \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)

=  \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)

= \(\dfrac{10+10+10+10+5}{10}\)

= \(\dfrac{\left(10+10+10+10\right)+5}{10}\)

= \(\dfrac{10\times4+5}{10}\)

= \(\dfrac{45}{10}\)

= \(\dfrac{9}{2}\)