a) 52 – 42 + 37 – 28 + 38 + 63 = (52 – 42) + (37 + 63) + (38 – 28) = 10 + 100 + 10 =  120

b) 130 + 35.19 – 9.70 – 30

= (35.19 – 9.70) + (130 – 30) = (35.19 – 9.35.2) + 100 = 35.(19 – 18) + 100 = 35 + 100 = 135

c) (11 + 13 + 15 + … + 19).(6.8 – 48) = (11+13+15+…+19).0 = 0

d) (72 – 8.9):(20+22+24 – 19 +21+23) = 0:(20+22+24 – 19 +21+23) = 0

Đè thừa một số \(\frac{25}{156}\),mk ko lại đề bài nhé

\(A=1-\frac{2+3}{2\cdot3}+.....+\frac{11+12}{11\cdot12}-\frac{12+13}{12\cdot13}\)

\(=1-\frac{1}{2}-\frac{1}{3}+\frac{1}{3}+\frac{1}{4}-...+\frac{1}{11}+\frac{1}{12}-\frac{1}{12}-\frac{1}{13}\)

\(=\frac{1}{2}-\frac{1}{13}=\frac{11}{26}\)

Thanks "Blue Moon" nhìu nha

bài 1 a)

\(\frac{15}{7}\times\frac43+\frac63\)

=\(\frac{60}{21}+\frac63\)

=\(\frac{60}{21}+\frac{42}{21}\)

=\(\frac{102}{21}\)

=\(\frac{34}{7}\)

b)\(\frac{-13}{41}\times\frac{17}{11}\times\frac{11}{17}\)

=\(\frac{-13}{41}\times\left(\frac{17}{11}\times\frac{11}{17}\right)\)

=\(\frac{-13}{41}\times1\)

=\(\frac{-13}{41}\)

Câu 1:

a) \(\dfrac{-15}{17}\) và \(\dfrac{-19}{21}\)

Ta có: \(\dfrac{-15}{17}=-1+\dfrac{2}{17}\); \(\dfrac{-19}{21}=-1+\dfrac{2}{21}\)

Vì \(\dfrac{2}{17}>\dfrac{2}{21}\)

Do đó: \(\dfrac{-15}{17}>\dfrac{19}{-23}\)

b) \(\dfrac{-13}{19}\) và \(\dfrac{19}{-23}\)

Ta có: \(\dfrac{19}{23}>\dfrac{19}{25}\); \(\dfrac{13}{19}=1-\dfrac{6}{19}\); \(\dfrac{19}{25}=1-\dfrac{6}{25}\)

mà \(\dfrac{6}{19}>\dfrac{6}{25}\) \(\Rightarrow\dfrac{13}{19}< \dfrac{19}{25}< \dfrac{19}{23}\)

Vì \(\dfrac{13}{19}< \dfrac{19}{23}\Rightarrow\dfrac{-13}{19}>\dfrac{19}{-23}\)

c) \(\dfrac{-24}{35}\) và \(\dfrac{-19}{30}\)

Ta có: \(\dfrac{-24}{35}=-1+\dfrac{19}{35}\);\(\dfrac{-19}{30}=-1+\dfrac{11}{30}\)

Vì \(\dfrac{11}{35}< \dfrac{11}{30}\)

Do đó: \(\dfrac{-24}{35}< \dfrac{-19}{30}\)

d) \(\dfrac{-1941}{1931}\) và \(\dfrac{-2011}{2001}\); \(\dfrac{-2011}{2001}=-1+\dfrac{10}{2001}\)

Vì \(\dfrac{10}{1931}< \dfrac{10}{1001}\)

Do đó: \(\dfrac{-1941}{1931}< \dfrac{-2011}{2001}\)

Ta có: \(\dfrac{-1941}{1931}=-1+\dfrac{10}{1931}\)

Sorry câu d mình viết ngược:

Làm lại:

d) \(\dfrac{-1941}{1931}\) và \(\dfrac{-2011}{2001}\)

Ta có: \(\dfrac{-1941}{1931}=-1+\dfrac{10}{1931};\)

\(\dfrac{-2011}{2001}=-1+\dfrac{10}{2001}\)

Vì \(\dfrac{10}{1931}< \dfrac{10}{1001}\)

Do đó: \(\dfrac{-1941}{1931}< \dfrac{-2011}{2001}\)

Trả lời

b)(1/3+12/67+13/41)-(79/67-28/41)

=1/3+12/67+13/41-79/67+28/41

=1/3+(12/67-79/67)+(13/41+28/41)

=1/3+(-67/67)+41/41

=1/3+(-1)+1

=1/3+0

=1/3.

c)38/45-(8/45-17/51-3/11)

=38/45-8/45+17/51+3/11

=30/45+1/3+3/11

=2/3+1/3+3/11

=3/3+3/11

=1+3/11

=1 3/11.

a/ \(\frac{15}{-50}=-\frac{3}{10}\)

\(\frac{7}{10}\)

\(\frac{24}{-20}=-\frac{12}{10}\)

\(\Rightarrow-\frac{12}{10};-\frac{3}{10};\frac{7}{10}\)

KL: ..........................................

b/ \(\frac{17}{39}=\frac{17.20}{39.20}=\frac{340}{780}\)

\(\frac{11}{65}=\frac{11.12}{65.12}=\frac{132}{780}\)

\(\frac{9}{52}=\frac{9.15}{52.15}=\frac{135}{780}\)

\(\Rightarrow\frac{132}{780};\frac{135}{780};\frac{340}{780}\)

KL:.............................................

c/ \(\frac{17}{20}=\frac{17.9}{20.9}=\frac{153}{180}\)

\(\frac{-19}{30}=-\frac{19.6}{30.6}=-\frac{114}{180}\)

\(\frac{38}{45}=\frac{38.4}{45.4}=\frac{152}{180}\)

\(\frac{-13}{18}=-\frac{13.10}{18.10}=-\frac{130}{180}\)

\(\Rightarrow-\frac{130}{180};-\frac{114}{180};\frac{152}{180};\frac{153}{180}\)

KL:..................................

1) A = \(\frac{-15}{19}.\frac{23}{37}+\frac{14}{37}.\frac{15}{19}=\frac{15}{19}.\frac{-23}{37}+\frac{14}{37}.\frac{15}{19}=\frac{15}{19}.\left(\frac{-23}{37}+\frac{14}{37}\right)=\frac{15}{19}.\frac{-9}{37}=\frac{-135}{703}\) 

TRẢ LỜI ĐI MAI CẦN NỘP !!!

A=19/20

\(A=\frac{3}{2}-\frac{5}{6}+\frac{7}{12}-\frac{9}{20}+\frac{11}{30}-\frac{13}{42}+\frac{15}{56}-\frac{17}{72}\)

\(=\left(1+\frac{1}{2}\right)-\left(\frac{1}{2}+\frac{1}{3}\right)+\left(\frac{1}{3}+\frac{1}{4}\right)-\left(\frac{1}{4}+\frac{1}{5}\right)+...-\left(\frac{1}{8}+\frac{1}{9}\right)\)

\(=1+\frac{1}{2}-\frac{1}{2}-\frac{1}{3}+\frac{1}{3}+\frac{1}{4}-\frac{1}{4}-\frac{1}{5}+\frac{1}{5}+\frac{1}{6}-...-\frac{1}{9}\)

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

\(=\frac{8}{9}\)