\(A=\frac{15}{90.94}+\frac{15}{94.98}+...+\frac{15}{146.150}\)

\(A=\frac{4}{4}\left(\frac{15}{90.94}+\frac{15}{94.98}+...+\frac{15}{146.150}\right)\)

\(A=\frac{15}{4}\left(\frac{4}{90.94}+\frac{4}{94.98}+...+\frac{4}{146.150}\right)\)

\(A=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+...+\frac{1}{146}-\frac{1}{150}\right)\)

\(A=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{150}\right)\)

\(A=\frac{15}{4}.\frac{1}{225}=\frac{1}{60}\)

\(B=\frac{6}{15.18}+\frac{6}{18.21}+...+\frac{6}{87.90}\)

\(B=\frac{3}{3}\left(\frac{6}{15.18}+\frac{6}{18.21}+...+\frac{6}{87.90}\right)\)

\(B=2\left(\frac{3}{15.18}+\frac{3}{18.21}+...+\frac{3}{87.90}\right)\)

\(B=2\left(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+...+\frac{1}{87}-\frac{1}{90}\right)\)

\(B=2\left(\frac{1}{15}-\frac{1}{90}\right)\)

\(B=2.\frac{1}{18}=\frac{1}{9}\)

Trả lời:

\(A=\frac{15}{90.94}+\frac{15}{94.98}+...+\frac{15}{146.150}\)

\(A=\frac{15}{4}.\left(\frac{4}{90.94}+\frac{4}{94.98}+...+\frac{4}{146.150}\right)\)

\(A=\frac{15}{4}.\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+...+\frac{1}{146}-\frac{1}{150}\right)\)

\(A=\frac{15}{4}.\left(\frac{1}{90}-\frac{1}{150}\right)\)

\(A=\frac{15}{4}.\frac{1}{225}\)

\(A=\frac{1}{60}\)

\(B=\frac{6}{15.18}+\frac{6}{18.21}+...+\frac{6}{87.90}\)

\(B=2.\left(\frac{3}{15.18}+\frac{3}{18.21}+...+\frac{3}{87.90}\right)\)

\(B=2.\left(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+...+\frac{1}{87}-\frac{1}{90}\right)\)

\(B=2.\left(\frac{1}{15}-\frac{1}{90}\right)\)

\(B=2.\frac{1}{18}\)

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

\(\frac{1-\frac{6}{23}+\frac{6}{31}-\frac{6}{154}}{\frac{5}{2}-\frac{15}{23}+\frac{15}{31}-\frac{15}{154}}\)

\(=\frac{\frac{6}{6}-\frac{6}{23}+\frac{6}{31}-\frac{6}{154}}{\frac{15}{6}-\frac{15}{23}+\frac{15}{31}-\frac{15}{154}}\)

\(=\frac{6\left(\frac{1}{6}-\frac{1}{23}+\frac{1}{31}-\frac{1}{154}\right)}{15\left(\frac{1}{6}-\frac{1}{23}+\frac{1}{31}-\frac{1}{154}\right)}\)

\(=\frac{6}{15}=\frac{2}{5}\)

mk sửa đề tí nhé

thanks'

Hack nao

b1: a, 6¹².(15+19-34)=6¹².0=0

b,4¹⁴.(37.4+23.4-240)=4¹⁴.0=0

c,(5¹⁷.125-5¹⁸.25)+6³:2³=(5¹⁷.5³-5¹⁸.5²)+3³=0+27=27

b2:a,143+7.(n-17)=206

===> 7.(n-17)=206-143=63

====>n-17=63:7=9

=====>n=9+17=26

vậy n=26

b,128-28:(15-n)=124

====>28:(15-n)=128-124=4

=====> 15-n=28:4=7

=====> n=15-7=8

vậy n=8

c,3ⁿ.2+48=210

====>3ⁿ.2=210-48=162

====>3ⁿ=162:2=81=3⁴

====>n=4

vậy n=4

a: \(=\left(\dfrac{2}{18}-\dfrac{15}{18}-\dfrac{72}{18}\right):\left(\dfrac{21}{36}-\dfrac{1}{36}-\dfrac{360}{36}\right)\)

\(=\dfrac{-85}{18}:\dfrac{-170}{18}\)

\(=\dfrac{85}{170}=\dfrac{1}{2}\)

b: \(=\left(\dfrac{5}{8}-\dfrac{5}{6}-\dfrac{5}{32}+\dfrac{5}{64}\right):\left(1-\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{8}\right)\)

\(=\dfrac{-55}{192}:\dfrac{3}{8}=\dfrac{-55}{192}\cdot\dfrac{8}{3}=-\dfrac{55}{72}\)

a) \(\frac{3^{15}.19+3^{15}.13}{3^{13}.16}\) =\(\frac{3^{15}.\left(19+13\right)}{3^{13}16}\) =\(\frac{3^{15}.32}{3^{13}.16}=\frac{3^{13}.3^2.32}{3^{13}.16}=\frac{3^2.2^4.2}{2^4}=18\)

Phần b bạn tự tách ra rồi nhóm lần lượt là ra mik chỉ làm phần a thôi nha

k cho mik nha

\(\frac{6}{13}-\frac{3}{26}=\frac{9}{26}\)

\(\frac{15}{12}+\frac{6}{24}=\frac{3}{2}\)

\(\frac{6}{13}-\frac{3}{26}=\frac{12}{26}-\frac{3}{26}=\frac{9}{26}\)

\(\frac{15}{12}+\frac{6}{24}=\frac{30}{24}+\frac{6}{24}=\frac{3}{2}\)

bài 1) a) \(1+2+3+4+........+2005+2006\)

\(\Leftrightarrow\) \(\left(1+2006\right)+\left(2+2005\right)+........+\left(1003+1004\right)\)

\(\Leftrightarrow\) \(2007.\dfrac{2006}{2}=2007.1003=2013021\)

b) \(5+10+15+.......+2000+2005\)

\(\Leftrightarrow\) \(\left(2005+5\right)\left(2000+10\right)+.......+\left(1000+1010\right)\)

\(\Leftrightarrow\) \(2010.\dfrac{2005}{5}=2010.401=405010\)

c) \(140+136+132+.......+64+60\)

\(\Leftrightarrow\) \(\left(140+60\right)+\left(136+64\right)+.......+\left(100+100\right)\)

\(\Leftrightarrow\) \(200.10\) = \(2000\)

1)

a) \(1+2+3+4+.....+2005+2006\)

Số các số hạng của dãy trên là:

\((2006-1):1+1=2006\)

Tổng dãy là:

\(\dfrac{2006\left(2006+1\right)}{2}=2013021\)

b) \(5+10+15+.....+2000+2005\)

Số các số hạng của dãy là:

\((2005-5):5+1=401\)

Tổng dãy là:

\(\dfrac{401\left(2005+5\right)}{2}=403005\)

c)\(140+136+132+.....+64+60\)

\(=60+64+.....+132+136+140\)

Số số hạng của dãy là:

\((140-60):4+1=11\)

Tổng dãy là:

\(\dfrac{11\left(60+140\right)}{2}=1100\)

Ta có:

\(\dfrac{-2}{15}-\dfrac{2}{15}:\left(1\dfrac{5}{6}-2\dfrac{1}{18}\right)\)

= \(\dfrac{-2}{15}\) - \(\dfrac{2}{15}:\left(\dfrac{11}{6}-\dfrac{37}{18}\right)\)

= \(\dfrac{-2}{15}-\dfrac{2}{15}:\left(\dfrac{33}{18}-\dfrac{37}{18}\right)\)

= \(\dfrac{-2}{15}-\dfrac{2}{15}:\dfrac{-2}{9}\)

= \(\dfrac{-2}{15}-\dfrac{2}{15}.\dfrac{9}{-2}\)

= \(\dfrac{-2}{15}-\dfrac{3}{-5}\)

= \(\dfrac{-2}{15}-\dfrac{-3}{5}\)

= \(\dfrac{-2}{15}-\dfrac{-9}{15}\)

= \(\dfrac{7}{15}\)

\(\dfrac{-2}{15}-\dfrac{2}{15}:\left(1\dfrac{5}{6}-2\dfrac{1}{18}\right)\)

\(=\dfrac{-2}{15}-\dfrac{2}{15}:\left(\dfrac{11}{6}-\dfrac{37}{18}\right)\)

\(=\dfrac{-2}{15}-\dfrac{2}{15}:\dfrac{-2}{9}=\dfrac{-2}{15}-\dfrac{9}{-15}=\dfrac{7}{15}\)