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B1:
a,\(\frac{-3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)\)
\(\Rightarrow\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}\)
\(\Rightarrow\left(\frac{-3}{7}+\frac{3}{7}\right)+\frac{15}{26}-\frac{4}{26}\)
\(\Rightarrow\frac{15}{26}-\frac{4}{26}\)
=\(\frac{11}{26}\)
b,\(\frac{23}{7}+\frac{2}{9}-\frac{13}{7}\)
\(=\frac{23}{7}-\frac{13}{7}+\frac{2}{9}\)
\(=\frac{10}{7}+\frac{2}{9}\)
\(=\frac{104}{63}\)
a: \(=\dfrac{-3}{7}+\dfrac{15}{26}-\dfrac{2}{13}+\dfrac{3}{7}=\dfrac{15}{26}-\dfrac{4}{26}=\dfrac{11}{26}\)
b: \(=\dfrac{6}{7}+\dfrac{2}{9}-\dfrac{10}{7}-5=\dfrac{-4}{7}-5+\dfrac{2}{9}=-\dfrac{337}{63}\)
c: \(=-\dfrac{11}{23}\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}=\dfrac{-22}{23}-\dfrac{1}{23}=-1\)
Bài 1 : Bỏ dấu ngoặc rồi thu gọn biểu thức:
a)A=(a+b)-(a-b)+(a-c)-(a+c)
= a + b - a + b + a - c - a - c
= ( a - a ) + ( b + b ) + ( a - a ) + ( - c - c )
= 0 + 2b + 0 + - 2c
= 2b - 2c
b)B=(a+b-c)+(a-b+c)-(b+c-a)-(a-b-c)
= a + b - c + a - b + c - b - c + a - a + b + c
= ( a - a ) + ( b - b ) + ( c - c ) + ( b - b ) + ( c - c ) + ( a + a )
= 0 + 0 + 0 + 0 + 0 + 2a
= 2a
Bài 2 :
a) thực hiện phép tính;
\(\left(-\frac{5}{28}+1,75+\frac{8}{35}\right):\left(-3\frac{9}{20}\right)\)
= \(\left(-\frac{5}{28}+\frac{7}{4}+\frac{8}{35}\right):\left(-\frac{69}{20}\right)\)
= \(\frac{9}{5}:\frac{-69}{20}=-\frac{12}{23}\)
b) tính nhanh
1) \(-\frac{3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)\)
= \(-\frac{3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}\)
= \(\left(\frac{-3}{7}+\frac{3}{7}\right)\) + \(\frac{15}{26}-\frac{2}{13}\)
= 0 + \(\frac{11}{26}=\frac{11}{26}\)
2) \(2.\frac{3}{7}+\left(\frac{2}{9}-1\frac{3}{7}\right)-\frac{5}{3}:\frac{1}{9}\)
= \(\frac{6}{7}+\left(\frac{2}{9}-\frac{10}{7}\right)-15\)
= \(\frac{6}{7}+\frac{2}{9}-\frac{10}{7}\) - 15
= \(\left(\frac{6}{7}-\frac{10}{7}\right)\) \(+\frac{2}{9}-15\)
= \(-\frac{4}{7}\) + \(\frac{2}{9}-15\)
= \(-\frac{967}{63}\)
Các câu 3 , 4 làm tương tự 2 câu trên nha em !
câu đố:
có một con chim đậu trên cành 2con khác bay đến đậu.Hỏi trên cành có bao nhiêu con chim?
a. \(\frac{-3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)=\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}=\frac{15}{13.2}-\frac{2}{13}=\frac{15}{13.2}-\frac{2.2}{13.2}=\frac{15-4}{26}=\frac{11}{26}\)
C. \(\frac{-11}{23}.\frac{6}{7}+\frac{8}{7}.\frac{-11}{23}-\frac{1}{23}=\frac{1}{23}.\left(-11.\frac{6}{7}-11.\frac{8}{7}-1\right)=\frac{1}{23}.\left(-22-1\right)=\frac{1}{23}.\left(-23\right)=-1\)
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
b/\(1\frac{2}{9}\)
Bài 1:
a) \(-\frac{3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)\)
\(=-\frac{3}{7}+\frac{15}{26}-\frac{4}{26}+\frac{3}{7}\)
\(=\left(-\frac{3}{7}+\frac{3}{7}\right)+\left(\frac{15}{26}-\frac{4}{26}\right)\)
\(=0+\frac{11}{26}\)
\(=\frac{11}{26}\)
b)\(2\frac{3}{7}+\frac{2}{9}-1\frac{3}{7}\)
\(=\frac{17}{7}+\frac{2}{9}-\frac{10}{7}\)
\(=\left(\frac{17}{7}-\frac{10}{7}\right)+\frac{2}{9}\)
\(=1+\frac{2}{9}\)
\(=1\frac{2}{9}=\frac{11}{9}\)
c)\(\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)
\(=\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{4}{24}-\frac{3}{24}-\frac{1}{24}\right)\)
\(=\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).0\)
\(=0\)