a)  6 4 5 − 1 2 3 + 3 4 5 = 6 4 5 − 3 4 5 − 1 2 3 = 3 − 5 3 = 4 3

b)  7 4 9 + 4 7 11 − 3 4 9 = 7 4 9 − 3 4 9 + 4 7 11 = 4 + 4 7 11 = 8 7 11

=(-259+259)+[(-74)+(-26)]+(-81+581)

=0+(-100)+500

=400

= -259 + 259 - 74 - 26 + 581 + 259 - 81
= 0 - 100 + 840 - 81
= 659

Mình bị nhầm :(( Tại bấm thêm số 259

349+8-2+349

Bài làm

   349 x 8 + 2 x 359

= 349 x ( 8 + 2 )

= 349 x 10

= 3490 

= 349 x (8 + 2)

= 349 x 10

= 3490

\(1\frac{13}{15}.0,75-\left(\frac{104}{195}+25\%\right).\frac{24}{47}-3\frac{12}{13}:3\)

\(=\frac{28}{15}.\frac{3}{4}-\left(\frac{8}{15}+\frac{1}{4}\right).\frac{8}{9}-\frac{51}{13}.\frac{1}{3}\)

\(=\frac{7}{5}-\left(\frac{32}{60}+\frac{15}{60}\right).\frac{8}{9}-\frac{17}{13}\)

\(=\frac{7}{5}-\frac{47}{60}.\frac{8}{9}-\frac{17}{13}\)

\(=\frac{7}{5}-\frac{94}{135}-\frac{17}{13}\)

\(=\frac{-212}{351}\)

Tự quy đồng

\(2\frac{3}{4}.\left(-0,4\right)-1\frac{3}{5}.2,75+\left(-1,2\right):\frac{4}{11}\)

\(=\frac{11}{4}.\frac{-2}{5}-\frac{8}{5}.\frac{11}{4}-\frac{6}{5}.\frac{11}{4}\)

\(=\frac{11}{4}.\left(\frac{-2}{5}-\frac{8}{5}-\frac{6}{5}\right)\)

\(=\frac{11}{4}.\frac{-16}{5}\)

\(=\frac{-44}{5}=-8\frac{4}{5}\)

\(=2.6\cdot\left(-2\right):2=2.6\cdot\left(-1\right)=-2.6\)

\(\dfrac{3}{7}.\left(\dfrac{-1}{9}\right)+\dfrac{3}{7}.\left(\dfrac{-2}{3}\right)\\ =\dfrac{3}{7}.\left(\dfrac{-1}{9}+\dfrac{-2}{3}\right)\\ =\dfrac{3}{7}.\dfrac{-7}{9}\\ =\dfrac{-21}{63}=\dfrac{-1}{3}\)

\(\dfrac{7}{2}-\left(\dfrac{3}{4}+\dfrac{1}{5}\right)\\ =\dfrac{7}{2}-\left(\dfrac{15}{20}+\dfrac{4}{20}\right)\\ =\dfrac{7}{2}-\dfrac{19}{20}\\ =\dfrac{70}{20}-\dfrac{19}{20}\\ =\dfrac{51}{20}\)

\(\left(\dfrac{1}{3}\right)^2.\dfrac{14}{11}-\dfrac{3}{11}\left(\dfrac{1}{3}\right)^2\\ =\dfrac{1}{9}.\dfrac{14}{11}-\dfrac{3}{11}.\dfrac{1}{9}\\ =\dfrac{1}{9}\left(\dfrac{14}{11}-\dfrac{3}{11}\right)\\ =\dfrac{1}{9}.\dfrac{11}{11}\\ =\dfrac{1}{9}.1\\ =\dfrac{1}{9`}\)