Tự luận bài 2:
\(\dfrac{x}{\dfrac{3}{50}}=\dfrac{\dfrac{2}{3}}{x}\\ \Rightarrow x.x=x^2=\dfrac{3}{50}.\dfrac{2}{3}=\dfrac{2}{50}=\dfrac{1}{25}=\left(\dfrac{1}{5}\right)^2 =\left(-\dfrac{1}{5}\right)^2\\ Nên:\left[{}\begin{matrix}x=\dfrac{1}{5}\\x=-\dfrac{1}{5}\end{matrix}\right.\\ Vậy:x=\pm\dfrac{1}{5}\)
trắc nghiệm
câu 1:C
câu 2: C
câu 3:C
câu 4:B
câu 5:A
Bài 1 TL:
\(2a=5b=3c\Rightarrow\dfrac{a}{\dfrac{1}{2}}=\dfrac{b}{\dfrac{1}{5}}=\dfrac{c}{\dfrac{1}{3}}\\ TCDTSBN:\dfrac{a}{\dfrac{1}{2}}=\dfrac{b}{\dfrac{1}{5}}=\dfrac{c}{\dfrac{1}{3}}.Và:a+b-c=-44\\ Nên:\dfrac{a+b-c}{\dfrac{1}{2}+\dfrac{1}{5}-\dfrac{1}{3}}=\dfrac{-44}{\dfrac{11}{30}}=-120\\ Vậy:\dfrac{a}{\dfrac{1}{2}}=-120\Rightarrow a=-60;\dfrac{b}{\dfrac{1}{5}}=-120\Rightarrow a=-24;\dfrac{c}{\dfrac{1}{3}}=-120\Rightarrow c=-40\)
