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\(C=\dfrac{-5}{7}+\dfrac{-2}{7}+\dfrac{3}{4}+\dfrac{1}{4}+\dfrac{-1}{5}=-1+1-\dfrac{1}{5}=\dfrac{-1}{5}\)
\(A=\frac{\left[\left(25-1\right):1+1\right]\left(25+1\right)}{2}=325.\)
\(B=\frac{\left[\left(51-3\right):2+1\right]\left(51+3\right)}{2}=675\)
\(C=\frac{\left[\left(81-1\right):4+1\right]\left(81+1\right)}{2}=861\)
a) e chỉ cần nhân chúng lại với nhau = cách tách từng cái ra
b)đặt 4/2.5+4/5.8+4/8.11+......+4/62.65 là S
\(.S=\frac{4}{3}\left(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{62.65}\right)\)
\(S=\frac{4}{3}\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{62}-\frac{1}{65}\right)\)
\(S=\frac{4}{3}\left(\frac{1}{2}-\frac{1}{65}\right)\)
\(S=\frac{4}{3}\left(\frac{65}{130}-\frac{2}{130}\right)\)
\(S=\frac{4}{3}\left(\frac{63}{130}\right)\)
\(S=\frac{42}{65}\)
Bài 2 : \(\frac{15+a}{29+a}=\frac{3}{5}\)\(\Leftrightarrow\left(15+a\right)5=\left(29+a\right)3\Leftrightarrow75+5a=87+3a\Leftrightarrow5a-3a=87-75\Rightarrow2a=12\Rightarrow a=6\)
vậy a =6
a)=1/2 . 8/15 - 3/4.47/9
=4/15 - 47/12
=-73/20
b)=2-1/3 . -21/20
=2+7/20
=47/20
a) \(\dfrac{1}{2}-\left(x+\dfrac{1}{3}\right)=\dfrac{5}{6}\)
\(\Rightarrow x+\dfrac{1}{3}=\dfrac{1}{2}-\dfrac{5}{6}\)
\(\Rightarrow x+\dfrac{1}{3}=\dfrac{-1}{3}\)
\(\Rightarrow x=\dfrac{-1}{3}-\dfrac{1}{3}\)
\(\Rightarrow x=\dfrac{-2}{3}\)
b)\(\dfrac{3}{4}-\left(x+\dfrac{1}{2}\right)=\dfrac{4}{5}\)
\(\Rightarrow x+\dfrac{1}{2}=\dfrac{3}{4}-\dfrac{4}{5}\)
\(\Rightarrow x+\dfrac{1}{2}=\dfrac{-1}{20}\)
\(\Rightarrow x=\dfrac{-1}{20}-\dfrac{1}{2}\)
\(\Rightarrow x=\dfrac{-11}{20}\)
c) \(\dfrac{3}{35}-\left(\dfrac{3}{5}+x\right)=\dfrac{2}{7}\)
\(\Rightarrow\dfrac{3}{5}+x=\dfrac{3}{35}-\dfrac{2}{7}\)
\(\Rightarrow\dfrac{3}{5}+x=\dfrac{-1}{5}\)
\(\Rightarrow x=\dfrac{-1}{5}-\dfrac{3}{5}\)
\(\Rightarrow x=\dfrac{-4}{5}\)
d)\(\dfrac{2}{3}.x=\dfrac{4}{27}\)
\(\Rightarrow x=\dfrac{4}{27}:\dfrac{2}{3}\)
\(\Rightarrow x=\dfrac{2}{9}\)
e) \(\dfrac{-3}{5}.x=\dfrac{21}{10}\)
\(\Rightarrow x=\dfrac{21}{10}:\dfrac{-3}{5}\)
\(\Rightarrow x=\dfrac{-7}{2}\)
\(\frac{-5}{6}\)\(+\)\(\frac{4}{9}\)\(\times\)\(\left(\frac{5}{4}-\frac{2}{3}\right)\)\(\times\)\(\left(-3\right)^2\)\(+\)\(\frac{5}{9}\)\(\times\)\(30\%\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{4}{9}\)\(\times\)\(\frac{7}{12}\)\(\times\)\(9\)\(+\)\(\frac{5}{9}\)\(\times\)\(\frac{3}{10}\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{7}{3}\)\(+\)\(\frac{5}{9}\)\(\times\)\(\frac{3}{10}\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{7}{3}\)\(+\)\(\frac{1}{6}\)
\(=\)\(\frac{-5}{6}\)\(+\)\(\frac{1}{6}\)\(+\)\(\frac{7}{3}\)
\(=\)\(\frac{-2}{3}\)\(+\)\(\frac{7}{3}\)
\(=\)\(\frac{5}{3}\)
\(125^3.25^4=25^9.25^4=25^{13}\)
\(16^2.64^5=4^4.4^{15}=4^{19}\)
to ko biet
tớ muốn cậu sửa lại đầu bài giùm cái
Nếu theo tớ thì đầu bài này là:
A=4+4^2+4^3+...+4^120
Cm a chia hết cho 5 đúng không hay là tính A chia cho 5 vậy