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A = 6/19 . -7/11 + 6/19 . -4/11 + -13/19
A = 6/19 . [-7/11 + (-4/11)] + (-13/19)
A = 6/19 . -11/11 + (-13/19)
A = 6/19 . (-1) + (-13/19)
A = -6/19 + (-13/19)
A = -19/19
A = -1
Vậy A = -1
Ta có: \(\dfrac{7}{13}\cdot\dfrac{5}{9}+\dfrac{7}{19}\cdot\dfrac{8}{13}-3\cdot\dfrac{7}{19}\)
\(=\dfrac{7}{13}\cdot\dfrac{5}{9}+\dfrac{7}{13}\cdot\dfrac{8}{19}-3\cdot\dfrac{7}{19}\)
\(=\dfrac{7}{13}\left(\dfrac{5}{9}+\dfrac{8}{19}\right)-3\cdot\dfrac{7}{19}\)
\(=\dfrac{7}{13}\cdot\dfrac{167}{171}-\dfrac{51}{19}\)
\(=\dfrac{-4798}{2223}\)
\(A=\dfrac{6}{19}.\dfrac{-7}{11}+\dfrac{6}{19}.\dfrac{-4}{11}+\dfrac{-13}{19}\)
\(A=\dfrac{6}{19}.\left(\dfrac{-7}{11}+\dfrac{-4}{11}\right)+\dfrac{-13}{19}\)
\(A=\dfrac{6}{19}.-1+\dfrac{-13}{19}=\dfrac{-6}{19}+\dfrac{-13}{19}=\dfrac{-19}{19}=-1\)
B=57.−413+57.73−513.37
B=57.−413+57.73− \(\dfrac{5}{7}.\dfrac{3}{13}\)3
7
\(B=\dfrac{5}{7}.\left(\dfrac{-4}{13}+\dfrac{7}{3}-\dfrac{3}{13}\right)\)
\(B=\dfrac{5}{7}.\dfrac{70}{39}=\dfrac{350}{273}\)
Câu B ko rõ lắm
\(B=\dfrac{5}{7}.\dfrac{-4}{13}+\dfrac{5}{7}.\dfrac{7}{3}-\dfrac{5}{13}.\dfrac{3}{7}\)
\(B=\dfrac{5}{7}.\dfrac{-4}{13}+\dfrac{5}{7}.\dfrac{7}{3}-\dfrac{5}{7}.\dfrac{3}{13}\)
Rồi tiếp 2 câu rõ
A=\(\dfrac{6}{19}\cdot\dfrac{-7}{11}+\dfrac{6}{19}\cdot\dfrac{-4}{11}+\dfrac{-13}{19}\)
= \(\dfrac{6}{19}\cdot\left(\dfrac{-7}{11}+\dfrac{-4}{11}\right)+\dfrac{-13}{19}\)(tính chất kết hợp)
=\(\dfrac{6}{19}\cdot-1+\dfrac{-13}{19}\)
=\(\dfrac{\left(-6\right)+\left(-13\right)}{19}\)
=\(\dfrac{-19}{19}=-1\)
B= \(\dfrac{5}{7}\cdot\dfrac{-4}{13}+\dfrac{5}{7}\cdot\dfrac{7}{13}-\dfrac{5}{13}\cdot\dfrac{3}{7}\)
=\(\dfrac{5}{7}\cdot\left(\dfrac{-4}{13}+\dfrac{7}{13}-\dfrac{3}{13}\right)\)( tính chất kết hợp)
=\(\dfrac{5}{7}\cdot0=0\)
a, \(\dfrac{14}{13}-\dfrac{1}{13}-\dfrac{19}{20}=1-\dfrac{19}{20}=\dfrac{1}{20}\)
b, \(-\dfrac{24}{17}+\dfrac{7}{17}+\dfrac{1}{16}=\dfrac{-17}{17}+\dfrac{1}{16}=-1+\dfrac{1}{16}=-\dfrac{15}{16}\)
c,
= \(\dfrac{5}{9}.\left(\dfrac{7}{13}+\dfrac{9}{13}+\dfrac{-3}{13}\right)\)
= \(\dfrac{5}{9}.1\)
= \(\dfrac{5}{9}\)
Gợi ý: Sử dụng tính chất phân phối của phép nhân đối với phép cộng để nhóm thừa số chung ra ngoài.
Sửa đề : \(-\dfrac{19}{37}=\dfrac{19}{37}\)
\(\dfrac{19}{37}-\dfrac{31}{24}-\dfrac{19}{37}+1\dfrac{7}{24}-\dfrac{2}{13}\)
\(=\dfrac{19}{37}-\dfrac{31}{24}+\dfrac{19}{37}+\dfrac{31}{24}-\dfrac{2}{13}\)
\(=\left(\dfrac{19}{37}-\dfrac{19}{37}\right)+\left(-\dfrac{31}{24}+\dfrac{31}{24}\right)-\dfrac{2}{13}=-\dfrac{2}{13}\)
Bài 1:
\(a,=\frac{2}{3}-\frac{16}{3}=\frac{-14}{3}\)
\(b,=\left(\frac{3}{7}+\frac{4}{7}\right)+\left(-\frac{6}{19}+\frac{-13}{19}\right)=1-1=0\)
\(c,=\frac{3}{5}.\left(\frac{8}{9}-\frac{7}{9}+\frac{26}{9}\right)=\frac{3}{5}.3=\frac{9}{5}\)
a,\(\dfrac{1}{2}\).\(\dfrac{4}{3}\)-\(\dfrac{20}{3}\).\(\dfrac{4}{5}\)=\(\dfrac{2}{3}\)-\(\dfrac{16}{3}\)=-\(\dfrac{14}{3}\)
\(P=\dfrac{1+19+\dfrac{19}{13}+\dfrac{19}{101}}{7+\dfrac{7}{13}+\dfrac{7}{19}+\dfrac{7}{101}}\)
\(=\dfrac{19\left(1+\dfrac{1}{3}+\dfrac{1}{19}+\dfrac{1}{101}\right)}{7\left(1+\dfrac{1}{13}+\dfrac{1}{19}+\dfrac{1}{101}\right)}=\dfrac{19}{7}\)