Bài 1: Ta chỉ cần bỏ ngoặc rồi cộng hai phân số để ra kết quả là số tự nhiên là xong

Bài 2:

A = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+............+\frac{1}{2003.2004}\)

A = \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-.............-\frac{1}{2003}+\frac{1}{2003}-\frac{1}{2004}\)

A = \(1-\frac{1}{2004}\)

A = \(\frac{2004}{2004}-\frac{1}{2004}=\frac{2003}{2004}\)

Mk làm mẫu 1 bài nha 

Bài 1 :

a, = (1/4+3/4) - (5/13+8/13)+2/11

    = 1 - 1 + 2/11

    = 2/11

Tk mk nha

Câu a:

(1/4 + -5/13) + (2/11 + -8/13 + 3/4)

= 1/4 - 5/13 + 2/11 - 8/13 + 3/4

= (1/4 + 3/4) - (5/13+ 8/13) + 2/11

= 1 - 1 + 2/11

= 0 + 2/11

= 2/11

Câu b:

(21/31 + -16/7) + (44/53 + 10/31) + 9/53

= 21/31 - 16/7 + 44/53 + 10/31 + 9/53

= (21/31 + 10/31) + (44/53 + 9/53) - 16/7

= 1 + 1 - 16/7

= 2 - 16/7

= -2/7

\(a,(\frac{1}{4}+\frac{-5}{13})+(\frac{2}{11}+\frac{-8}{13}+\frac{3}{4})\)

\(= (\frac{1}{4} + \frac{3}{4}) + (\frac{-5}{13} + \frac{-8}{13}) + \frac{2}{11}\)

\(= \frac{4}{4} + \frac{-13}{13} + \frac{2}{11}\)

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

\(b,(\frac{21}{31}+\frac{-16}{7})+(\frac{44}{53}+\frac{10}{31})+\frac{9}{53}\)

\(= (\frac{21}{31} + \frac{10}{31}) + (\frac{44}{53} + \frac{9}{53}) + \frac{-16}{7}\)

\(=\frac{31}{31}+\frac{53}{53}+\frac{-16}{7}=1+1-\frac{16}{7}\)

\(=2-\frac{16}{7}=\frac{14}{7}-\frac{16}{7}=-\frac27\)

\(c,\frac{-5}{7}+\frac{3}{4}+\frac{-1}{5}+\frac{-2}{7}+\frac{1}{4}\)

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

\(= \frac{-7}{7} + \frac{4}{4} + \frac{-1}{5}\)

\(=-1+1-\frac{1}{5}=0-\frac15=-\frac15\)

\(\frac{-3}{31} + \frac{-6}{17} + \frac{1}{25} + \frac{-28}{31} + \frac{-11}{17} + \frac{-1}{5}\)

\(= (\frac{-3}{31} + \frac{-28}{31}) + (\frac{-6}{17} + \frac{-11}{17}) + \frac{1}{25} + \frac{-1}{5}\)

\(= \frac{-31}{31} + \frac{-17}{17} + \frac{1}{25} - \frac{5}{25}\)

\(= -1 + (-1) + \frac{-4}{25}\)

\(=-2-\frac{4}{25}=-\frac{50}{25}-\frac{4}{25}=-\frac{54}{25}\)

a,  -3/4 + 3/7 + -1/4 + 4/9 + 4/7

=\(\left(\frac{-3}{4}+\frac{-1}{4}\right)+\left(\frac{3}{7}+\frac{4}{7}\right)+\frac{4}{9}\)

=\(-1+1+\frac{4}{9}\)

=\(\frac{4}{9}\)

b, -7/9 x 4/11 + -7/9 x 7/11 + 5 và 7/9 

\(=\frac{7}{9}x\frac{-4}{11}+\frac{7}{9}x\frac{-7}{11}+5x\frac{7}{9}\)

\(=\frac{7}{9}x\left(\frac{-4}{11}+\frac{-7}{11}+5\right)\)

\(=\frac{7}{9}x4\)

\(=\frac{28}{9}\)

c, ( 21/31 + 2013/6039 ) - ( 44/53 - 10/31) - /53

a)(1/4+3/4)-(5/13+8/13)+2/11=1-1+2/11=2/11

b)(21/31+10/31)-16/7+(44/53+9/53)=1+1-16/7=14/7-16/7=-2/7

bằng2/11

         -16/7

Câu 1:

\(=\dfrac{21}{31}+\dfrac{1}{3}-\dfrac{44}{53}+\dfrac{10}{31}-\dfrac{9}{53}=\dfrac{1}{3}\)

Câu 2:

1: =>1,3x=-1,31

=>130x=-131

=>x=-131/130

2: =>(4,5-2x)=11/14:(-11/7)=-7/14=-1/2=-0,5

=>2x=5

=>x=5/2

Câu a:

(1/4 + -5/13) + (2/11 + -8/13 + 3/4)

= 1/4 - 5/13 + 2/11 - 8/13 + 3/4

= (1/4 + 3/4) - (5/13+ 8/13) + 2/11

= 1 - 1 + 2/11

= 0 + 2/11

= 2/11

Câu b:

Câu b:

(21/31 + -16/7) + (44/53 + 10/31) + 9/53

= 21/31 - 16/7 + 44/53 + 10/31 + 9/53

= (21/31 + 10/31) + (44/53 + 9/53) - 16/7

= 1 + 1 - 16/7

= 2 - 16/7

= -2/7

a,  -3/4 + 3/7 + -1/4 + 4/9 + 4/7

=

=

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