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BÀI 1
a, \(5\times\frac{-7}{10}=\frac{-35}{10}=\frac{-7}{2}\)
b, \(\frac{4}{5}\times\frac{-7}{10}=\frac{-28}{50}=\frac{-14}{25}\)
c, \(\frac{4}{9}+\frac{4}{3}\times\frac{16}{4}=\frac{4}{9}+\frac{16}{3}=\frac{52}{9}\)
d, \(\frac{11}{22}-\frac{3}{9}\times\frac{14}{21}=\frac{11}{22}-\frac{2}{9}=\frac{55}{198}=\frac{5}{18}\)
BÀI 2
\(A=\frac{6}{13}\times\frac{5}{7}+\frac{6}{13}\times\frac{2}{7}+\frac{17}{13}\)
\(A=\frac{30}{91}+\frac{12}{91}+\frac{17}{13}\)
\(A=\frac{30}{91}+\frac{12}{91}+\frac{119}{91}\)
\(A=\frac{161}{91}=\frac{23}{13}\)
\(B=\frac{11}{15}\times\frac{4}{11}+\frac{11}{15}\times\frac{5}{11}+\frac{11}{15}\times\frac{2}{11}\)
\(B=\frac{4}{15}+\frac{1}{3}+\frac{2}{15}\)
\(B=\frac{11}{15}\)
\(C=\left(\frac{19}{64}-\frac{33}{22}+\frac{24}{51}\right)\times\left(\frac{1}{5}-\frac{1}{15}-\frac{2}{15}\right)\)
\(C=\frac{-797}{1088}\times0\)
\(C=0\)
\(D=\frac{8}{13}\times\frac{7}{12}+\frac{8}{13}\times\frac{5}{12}-\frac{1}{12}\)
\(D=\frac{14}{39}+\frac{10}{39}-\frac{1}{12}\)
\(D=\frac{83}{156}\)
bạn biết câu náy không (24 + 11) . {546 - [14 . (64 - 2^{3}3) : 2]} =
a)\(\dfrac{-6}{11}:\left(\dfrac{3}{5}.\dfrac{4}{11}\right)=\dfrac{-5}{2}\)
b)\(\dfrac{7}{12}+\dfrac{5}{12}:6-\dfrac{14}{30}=\dfrac{67}{370}\)
c)\(\left(\dfrac{4}{5}+\dfrac{1}{2}\right):\left(\dfrac{3}{13}-\dfrac{8}{13}\right)=-\dfrac{169}{50}\)
d)\(\left(\dfrac{2}{3}-\dfrac{1}{4}+\dfrac{5}{11}\right):\left(\dfrac{5}{12}+1-\dfrac{7}{11}\right)=\dfrac{115}{103}\)
Mình làm mẫu 1 bài rùi bạn tự giải những bài còn lại nha
1, 7A = 7+7^2+7^3+....+7^2008
6A = 7A - A = (7+7^2+7^3+....+7^2008)-(1+7+7^2+....+7^2007) = 7^2008-1
=> A = (7^2008-1)/6
Tk mk nha
\(A=1+7+7^2+7^3+...+7^{2007}\)
\(\Rightarrow7A=7+7^2+7^3+7^4+...+7^{2008}\)
\(\Rightarrow7A-A=\left(7+7^2+7^3+...+7^{2008}\right)-\left(1+7+7^2+...+7^{2007}\right)\)
\(\Rightarrow6A=7^{2008}-1\)
\(\Rightarrow A=\frac{7^{2008}-1}{6}\)
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
a, \(-\dfrac{3}{7}\times\dfrac{15}{13}-\dfrac{3}{7}\times\dfrac{11}{13}-\dfrac{3}{7}\)
\(=-\dfrac{3}{7}\times\left(\dfrac{15}{13}+\dfrac{11}{13}+1\right)\)
\(=-\dfrac{3}{7}\times\left(\dfrac{26}{13}+1\right)\)
\(=-\dfrac{3}{7}\times\left(2+1\right)\)
\(=-\dfrac{3}{7}\times3=-\dfrac{9}{7}\)
b, \(\dfrac{5}{6}+\dfrac{1}{6}:\dfrac{4}{3}\)
\(=\dfrac{5}{6}+\dfrac{1}{6}\times\dfrac{3}{4}\)
\(=\dfrac{20}{24}+\dfrac{3}{24}=\dfrac{23}{24}\)
c, \(\left(\dfrac{5}{7}-\dfrac{3}{4}\right)-\dfrac{7}{4}\)
\(=\dfrac{5}{7}-\dfrac{3}{4}-\dfrac{7}{4}\)
\(=\dfrac{5}{7}-\left(\dfrac{3}{4}+\dfrac{7}{4}\right)\)
\(=\dfrac{5}{7}-\dfrac{10}{4}\)\(=\dfrac{5}{7}-\dfrac{5}{2}\)
\(=\dfrac{10}{14}-\dfrac{35}{14}=\dfrac{-25}{14}\)
d, \(-\dfrac{6}{5}-\dfrac{2}{3}=-\dfrac{18}{15}-\dfrac{10}{15}=-\dfrac{28}{15}\)
e, \(\dfrac{3}{4}+\dfrac{1}{4}:\left(1-\dfrac{1}{4}\right)\)
\(=\dfrac{3}{4}+\dfrac{1}{4}:\dfrac{3}{4}\)
\(=\dfrac{3}{4}+\dfrac{1}{4}\times\dfrac{4}{3}\)
\(=\dfrac{3}{4}+\dfrac{1}{3}=\dfrac{9}{12}+\dfrac{4}{12}=\dfrac{13}{12}\)
f, \(-\dfrac{3}{8}\times\dfrac{12}{13}-\dfrac{3}{8}\times\dfrac{14}{13}\)
\(=-\dfrac{3}{8}\times\left(\dfrac{12}{13}+\dfrac{14}{13}\right)\)
\(=-\dfrac{3}{8}\times\dfrac{26}{13}\)\(=-\dfrac{3}{8}\times2=-\dfrac{6}{8}\)
a)= \(\dfrac{-9}{7}\)
b)= \(\dfrac{23}{34}\)
c)=-\(\dfrac{5}{3}\)
d)=-28/15