\(\dfrac{1}{6}+\dfrac{-2}{5}=\dfrac{5}{30}+\dfrac{-12}{30}=\dfrac{-7}{30}\)

\(\dfrac{5}{12}-\dfrac{7}{8}=\dfrac{10}{24}-\dfrac{21}{24}=\dfrac{-11}{24}\)

\(\dfrac{-4}{25}:\dfrac{-32}{45}=\dfrac{-4}{25}.\dfrac{-45}{32}=\dfrac{-1}{5}.\dfrac{-9}{8}=\dfrac{4}{40}\)

\(\dfrac{-2}{9}.\dfrac{7}{11}+\dfrac{-2}{9}.\dfrac{10}{11}+\dfrac{-2}{9}.\dfrac{5}{11}=\dfrac{-2}{9}\left(\dfrac{7}{11}+\dfrac{10}{11}+\dfrac{5}{11}\right)=\dfrac{-2}{9}.\dfrac{22}{11}=\dfrac{-2}{9}.2=\dfrac{-4}{9}\)

A, 5/6 + 13/6 = 3

B, 9/16 - 3/8 = 3/16

C, 2/9 x 5/3 = 10/27

D, 4/6 + 7/3 x 5/2 = 13/2

a) 3

b)3/16

c)10/27

d)13/2

bài 1: 

\(2\dfrac{3}{4}:1\dfrac{1}{3}=\dfrac{11}{4}:\dfrac{4}{3}=\dfrac{33}{16}\)

bài 2 mk lười làm, he he

xàm??

.-. ?

spam à

5: \(=3-\dfrac{1}{4}+\dfrac{2}{3}-5+\dfrac{1}{3}+\dfrac{6}{5}-6+\dfrac{7}{4}-\dfrac{3}{2}\)

\(=3-5-6+\dfrac{-1}{4}+\dfrac{7}{4}+\dfrac{2}{3}+\dfrac{1}{3}+\dfrac{6}{5}-\dfrac{3}{2}\)

\(=-8+\dfrac{3}{2}+1+\dfrac{-3}{10}\)

\(=-7+\dfrac{15-3}{10}=-7+\dfrac{6}{5}=-\dfrac{29}{5}\)

6: \(=6-\dfrac{2}{3}+\dfrac{1}{2}-5-\dfrac{5}{3}+\dfrac{3}{2}-3+\dfrac{7}{3}-\dfrac{5}{2}\)

\(=6-5-3-\dfrac{2}{3}-\dfrac{5}{3}+\dfrac{7}{3}+\dfrac{1}{2}+\dfrac{3}{2}-\dfrac{5}{2}\)

\(=-2-\dfrac{1}{2}=-\dfrac{5}{2}\)

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

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

=-3+1

=-2

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

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

\(=11+2-1-\dfrac{1}{2}\)

=11+1/2

=11,5

14dm5cm=14,5dm;3dm7cm=3,7dm

chu vi hình chữ nhật đó là:

(14,5+3,7)x2=36,4(dm)

ĐS:36,4dm

14 dm 5 cm = 14,5 dm 

3 dm 7 cm = 3,7 dm 

Chiều rộng HCN là :

14,5 - 3,7 = 10,8 ( dm )

chu vi HCN là :

( 14,5 + 10,8 ) x 2 = 50,6 ( dm )

ĐS:..

Lời giải chi tiết:

2=1+1          6=2+4          8=5+3          10=8+2

3=1+2          6=3+3          8=4+4          10=7+3

4=3+1          7=6+1          9=8+1          10=6+4

4=2+2          7=5+2          9=7=2          10=5+5

5=4+1          7=4+3         9=6+3           10=10+0

5=3+2          8=7+1         9=5=4           10=0+10

6=5+1          8=6=2         10=9+1         1=0+1