\(Taco:\)

\(\left(x+y\right)\left(y+z\right)=187\Leftrightarrow xy+xz+yy+yz=187\)

\(\left(y+z\right)\left(z+x\right)=154\Leftrightarrow yz+xy+zz+xz=154\)

\(\left(z+x\right)\left(x+y\right)=238\Leftrightarrow xz+zy+xx+xy=238\)

\(\Rightarrow\left(x+y\right)\left(y+z\right)+\left(x+z\right)\left(x+y\right)+\left(y+z\right)\left(z+x\right)=579\)

\(\Leftrightarrow xy+zx+yy+yz+yz+xy+zz+xz+xz+zy+xx+xy=579\)

\(\Leftrightarrow3\left(xz+xy+yz\right)+x^2+y^2+z^2=579\)

\(\left(z+x\right)\left(x+y\right)-\left(x+y\right)\left(y+z\right)=51\)

\(\Leftrightarrow\left(x+y\right)\left(x-y\right)=x^2-y^2=51\)

\(\left(z+x\right)\left(x+y\right)-\left(y+z\right)\left(x+z\right)=84\)

\(\Leftrightarrow\left(x+z\right)\left(x-z\right)=84\Leftrightarrow x^2-z^2=84\)

\(\Leftrightarrow y^2-z^2=33\)

đến đây tịt

ak tớ bt cách giải rồi cần thì ib ns tớ lm :v

\(\hept{\begin{cases}2x-y+2y=1\\3x+y+x=3\end{cases}}\)

\(\hept{\begin{cases}2x+y=1\\4x+y=3\end{cases}}\)\(\hept{\begin{cases}y=1-2x\\4x+y=3\end{cases}}\)\(\hept{\begin{cases}y=1-2x\\4x+1-2x=3\end{cases}}\)\(\hept{\begin{cases}y=1-2x\\2x+1=3\end{cases}}\)

\(\hept{\begin{cases}y=1-2x\\x=1\end{cases}}\)\(\hept{\begin{cases}y=-1\\x=1\end{cases}}\)

299.792.458 m/s. 
300.000km/s 

câu 1 bạn có cho đề sai ko :

bạn có thể kham khảo bài ;

https://olm.vn/hoi-dap/detail/203671433762.html

Có thể là $\frac{{{a}^{2}}b}{2a+b}+\frac{{{b}^{2}}c}{2b+c}+\frac{{{c}^{2}}a}{2c+a}\le 1$