Tính:
\(\dfrac{63}{8}+5\dfrac{1}{2}\)
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\(A=-5,13:\left(5\dfrac{5}{28}-1\dfrac{8}{9}.1,25+1\dfrac{16}{63}\right)\)
\(=-5,13:\left(5\dfrac{5}{28}-2\dfrac{13}{36}+1\dfrac{16}{63}\right)\)
\(=5,13:\left[\left(5-2+1\right)+\left(\dfrac{5}{28}-\dfrac{13}{36}+\dfrac{16}{63}\right)\right]\)
\(=5,13:\left(4+\dfrac{1}{14}\right)\)
\(=1,26\)
1: \(=\dfrac{1}{2}\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{11}-\dfrac{1}{13}\right)\)
=1/2*10/39
=5/39
2: \(=\dfrac{5}{2}\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{9}-\dfrac{1}{11}\right)=\dfrac{5}{2}\cdot\dfrac{10}{11}=\dfrac{50}{22}=\dfrac{25}{11}\)
\(PTK_{^{65}Cu^{16}O}=65+16=81\left(đ.v.C\right)\\ PTK_{^{65}Cu^{17}O}=65+17=82\left(đ.v.C\right)\\ PTK_{^{65}Cu^{18}O}=65+18=83\left(đ.v.C\right)\\ PTK_{^{63}Cu^{16}O}=63+16=79\left(đ.v.C\right)\\ PTK_{^{63}Cu^{17}O}=63+17=80\left(đ.v.C\right)\\ PTK_{^{63}Cu^{18}O}=63+18=81\left(đ.v.C\right)\)
a)\(=\dfrac{211}{180}\)
b)\(=\dfrac{5}{39}\)
c)=\(=-\dfrac{65}{168}\)
\(-1,53:\left(5\dfrac{5}{28}-1\dfrac{8}{9}\cdot1.25+1\dfrac{16}{63}\right)\)
\(=-\dfrac{153}{100}:\left(\dfrac{145}{28}-\dfrac{17}{9}\cdot\dfrac{5}{4}+\dfrac{79}{63}\right)\)
\(=-\dfrac{153}{100}:\left(\dfrac{145}{28}-\dfrac{85}{36}+\dfrac{79}{63}\right)\)
\(=-\dfrac{153}{100}:\dfrac{1395-595+316}{252}\)
\(=-\dfrac{153}{100}\cdot\dfrac{252}{1116}=\dfrac{-153}{100}\cdot\dfrac{7}{31}=\dfrac{-1071}{3100}\)
\(\dfrac{63}{8}+5\dfrac{1}{2}\)
\(=\dfrac{63}{8}+\dfrac{11}{2}\)
\(=\dfrac{63}{8}+\dfrac{44}{8}\)
\(=\dfrac{107}{8}\)