\(a\div b=2\div5\Rightarrow a=\frac{2}{5}b\)
\(b\div c=4\div3\Rightarrow c=\frac{3}{4}b\)
\(ab-c^2=-10,4\)
\(\Leftrightarrow\frac{2}{5}b.b-\left(\frac{3}{4}b\right)^2=-10,4\)
\(\Leftrightarrow\frac{-13}{80}b^2=-10,4\)
\(\Leftrightarrow b^2=64\)
\(\Leftrightarrow\orbr{\begin{cases}b=8\Rightarrow a=\frac{16}{5},c=6\\b=-8\Rightarrow a=\frac{-16}{5},c=-6\end{cases}}\)
\(\left|a+b+c\right|=\left|8+\frac{16}{5}+6\right|=\frac{86}{5}=17,2\)
=17,2 hok tốt
