\(5+5=10\)

Who often do the washing in your house ? 

\(n_{H_2SO_4}=0,15.0,3=0,045\left(mol\right)\)

\(R_2O_3+3H_2SO_4\rightarrow R_2\left(SO_4\right)_3+3H_2O\)

   0,015 <----  0,045                                 /mol

\(M=\dfrac{2,4}{0,015}=160=2R+48\)  \(\Rightarrow R=56\)  \(\Rightarrow R\) là Fe

=> CTHH : \(Fe_2O_3\)

\(\dfrac{2}{5}=\dfrac{1}{2,5}\)

Chọn C 

15% của 150 kg là : \(150.15\%=22,5\left(kg\right)\)

Đ/s:...

It is he that likes playing football

\(10-x=46,8:6,5\Leftrightarrow10-x=7,2\Leftrightarrow x=2,8\)

Chọn A 

\(a+b+c=0\Leftrightarrow\left(a+b+c\right)^2=0\Leftrightarrow a^2+b^2+c^2+2\left(ab+bc+ac\right)=0\)

\(\Leftrightarrow14+2\left(ab+bc+ac\right)=0\Leftrightarrow ab+bc+ac=-7\)

Suy ra : \(\left(ab+bc+ac\right)^2=49\Leftrightarrow a^2b^2+b^2c^2+a^2c^2+2abc\left(a+b+c\right)=49\)

\(\Leftrightarrow a^2b^2+b^2c^2+a^2c^2=49\)

\(a^2+b^2+c^2=14\Leftrightarrow\left(a^2+b^2+c^2\right)^2=196\Leftrightarrow a^4+b^4+c^4+2\left(a^2b^2+b^2c^2+a^2c^2\right)=196\)

\(\Leftrightarrow a^4+b^4+c^4+2.49=256\)  \(\Leftrightarrow a^4+b^4+c^4=98\)

Vậy ... 

\(\dfrac{16}{24}+\dfrac{10}{9}.\dfrac{27}{11}=\dfrac{2}{3}+\dfrac{30}{11}=\dfrac{22+90}{33}=\dfrac{112}{33}\)