Cách 1:

A=(3+ 1/2 -2/3 ) -( 2- 2/3 +5/2) - (5- 5/2 + 4/3)

A=17/6-23/6-23/6

A=-29/6

Cách 2:

A=(3+ 1/2 -2/3 ) -( 2- 2/3 +5/2) - (5- 5/2 + 4/3)

A=3+ 1/2 -2/3 - 2+ 2/3 -5/2 - 5+ 5/2 - 4/3

A=-29/6

cách 1:

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

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

\(=\frac{-24}{6}+\frac{3}{6}-\frac{8}{6}=-\frac{29}{6}\)

cách 2:

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

\(=\left(\frac{18}{6}+\frac{3}{6}-\frac{4}{6}\right)-\left(\frac{12}{6}-\frac{4}{6}+\frac{15}{6}\right)-\left(\frac{30}{6}-\frac{15}{6}+\frac{8}{6}\right)\)

\(=\frac{17}{6}-\frac{23}{6}-\frac{23}{6}=-\frac{29}{6}\)

a) c1 := -2/-5+-5/-6+4/5

=2/5+5/6+4/5

=12/30+25/30+24/30

=61/30

c2:=(2/5+4/5)+4/5

=(2/5+4/5)+5/6

=6/5+5/6

=36/30+25/30

=61/30

b)c1:=-3/-4+11/-15+-1/2

=3/4+-11/15+-1/2

=45/60+-44/30+-30/60

-29/30

c2:=3/4+(-11/15+-1/2)

=(3/4+-1/2)+-11/15

=(3/4+-2/4)+-11/5

=1/4+-11/15

=15/60+-44/60

=-29/60

\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}:\dfrac{1}{5}+\dfrac{3}{5}.\dfrac{1}{3}\)

=\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}.\dfrac{5}{1}+\dfrac{3}{5}.\dfrac{1}{3}\)

=\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{3}+\dfrac{3}{5}.\dfrac{1}{3}\)

=\(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{1}{3}.2+\dfrac{3}{5}.\dfrac{1}{3}\)

=\(\dfrac{1}{3}.\left(\dfrac{2}{5}+\dfrac{3}{5}-2\right)\)=\(\dfrac{1}{3}.\left(-1\right)=\dfrac{-1}{3}\)

\(\left(4-\dfrac{5}{12}\right):2+\dfrac{5}{24}\)

=\(\left(4-\dfrac{5}{12}\right).\dfrac{1}{2}+\dfrac{5}{24}\)

=\(4.\dfrac{1}{2}-\dfrac{5}{12}.\dfrac{1}{2}+\dfrac{5}{24}\)

=\(2-\dfrac{5}{24}+\dfrac{5}{24}=2\)

1: =(-20/36+15/36)*(-3/10)+(-16/36+21/36)

=-5/36*(-3/10)+5/36

=5/36*13/10

=65/360=13/72

2: Bạn xem lại đề nha bạn, dãy số này không có quy luật nào hết luôn á

a: =8/20-5/20+6/20=9/20

b: =-2/5:9/10=-2/5*10/9=-20/45=-4/9

c: =7/8*4/9+1/14*14/5

=28/72+1/5

=53/90

d: =2/7(3/11+8/11)

=2/7

-1/2+ 2/3 - 3/4 + 4/5

trả lời:

-1/2+ 2/3 - 3/4 + 4/5

=13/60

\(1-\frac{1}{2}+2-\frac{2}{3}+3-\frac{3}{4}+4-\frac{1}{4}-3-\frac{1}{3}-2-\frac{1}{2}-1\)

\(=\left(1+2+3+4-3-2-1\right)+\left(-\frac{1}{2}-\frac{2}{3}-\frac{3}{4}-\frac{1}{4}-\frac{1}{3}-\frac{1}{2}\right)\)

\(=4+\left[\left(-\frac{1}{2}-\frac{1}{2}\right)+\left(-\frac{2}{3}-\frac{1}{3}\right)+\left(-\frac{3}{4}-\frac{1}{4}\right)\right]\)

\(=4+\left[\left(-1\right)+\left(-1\right)+\left(-1\right)\right]\)

\(=4+\left(-3\right)=1\)

\(1-\frac{1}{2}+2-\frac{2}{3}+3-\frac{3}{4}+4-\frac{1}{4}-3-\frac{1}{3}-2-\frac{1}{2}-1\)

\(=\left(1-1\right)+\left(2-2\right)+\left(3-3\right)+4-\left(\frac{1}{2}+\frac{1}{2}\right)-\left(\frac{2}{3}+\frac{1}{3}\right)-\left(\frac{3}{4}+\frac{1}{4}\right)\)

\(=4-1-1-1\)

\(=1\)

  13 - 12 + 11 - 10 - 9 + 8 - 7 - 6 + 5 - 4 + 3 + 2 - 1 
= ( 13 - 12 + 11 - 10 + 8 ) - ( 9 + 1 ) - ( 6 + 4) + ( 3 + 2 + 5 ) - 7 
= 10 - 10 - 10 + 10 - 7 
= ( 10 - 10 ) - ( 10 - 10 ) - 7 
= 0 - 0 - 7 
= - 7

\(13-12+11+10-9+8-7-6+5-4+3+2-1\)

\(=\left(13-12+11-10+8\right)-\left(9+1\right)-\left(6+4\right)+\left(3+2+5\right)-7\)

\(=10-10-10+10-7\)

\(=-7\)