Đáp án:
\(D=\dfrac{111}{20}\) hoặc \(D=-\dfrac{105}{4}\)
Giải thích các bước giải:
Theo đề: \(|x|=0,6\)
\(\Leftrightarrow \) \(\left[ \begin{array}{l}x=0,6\\x=-0,6\end{array} \right.\)
TH1: \(x=0,6\)
\(D=6,25.(0,6)^{2} -4(0,6-2,25):(0,8+2.0,6)=\dfrac{25}{4}.\dfrac{9}{25}+4.\dfrac{33}{20}:2=\dfrac{9}{4}+\dfrac{33}{10}=\dfrac{111}{20}\)
TH2: \(x=-0,6\)
\(D=6,25.(-0,6)^{2} -4(-0,6-2,25):(0,8+2.(-0,6))=\dfrac{25}{4}.\dfrac{9}{25}+4.\dfrac{57}{20}:(-\dfrac{2}{5})=\dfrac{9}{4}-\dfrac{57}{2}=-\dfrac{105}{4}\)
