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\(\dfrac{x+1}{10}+\dfrac{x+1}{11}+\dfrac{x+1}{12}=\dfrac{x+1}{14}+\dfrac{x+1}{15}\)
\(\Leftrightarrow\left(x+1\right)\left(\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}-\dfrac{1}{14}-\dfrac{1}{15}\right)=0\)
=>x+1=0
hay x=-1
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{0,4-\dfrac{2}{9}+\dfrac{2}{11}}{1,4-\dfrac{7}{9}+\dfrac{7}{11}}-\dfrac{\dfrac{1}{3}-0,25+\dfrac{1}{5}}{1\dfrac{1}{6}-0,875+0,7}\\ =\dfrac{2\left(0,2-\dfrac{1}{9}+\dfrac{1}{11}\right)}{7\left(0,2-\dfrac{1}{9}+\dfrac{1}{11}\right)}-\dfrac{2\left(\dfrac{1}{6}-0,125+0,1\right)}{7\left(\dfrac{1}{6}-0,125+0,1\right)}\\ =\dfrac{2}{7}-\dfrac{2}{7}\\ =0\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(D=\left\{x=\left(3n\right)^2|n\in N;1\le n\le4\right\}\)
\(C=\left\{x=\left(-3\right)^n|n\in N;1\le n\le4\right\}\)
\(E=\){x\(\in N^{''}|x\) là các số nguyên tố \(\le\)11}
G={x=\(\dfrac{1}{n+n^2}|n\in N'';n\le5\)}
\(H=\left\{x=\dfrac{3}{3^n}|n\in N'';n\le5\right\}\)
N'' là N sao đó
![](https://rs.olm.vn/images/avt/0.png?1311)
D={x=k2;3<=k<=12; k chia hết cho 3}
E={x=(-3)k;1<=k<=4}
G={1/x(x+1);x∈N;1<=x<=5}
![](https://rs.olm.vn/images/avt/0.png?1311)
\(-12;-9;-8;\frac{-7}{2};\frac{-21}{16};\frac{-11}{9};-\frac{1}{2}\)
no no on onnonoonon
? mình không hiểu nhé