by Tìm \(x\):
a. \(\frac{-1}{2}:(2x-1)=0,2:\frac{-3}{5}\)
b. \(\frac{16}{x}=\frac{x}{25}\)
c. \(\frac{3}{1-2x}=\frac{-5}{3x-2}\)
Phương pháp giải:
Phương pháp:
Áp dụng tính chất của tỉ lệ thức \(\frac{a}{b}=\frac{c}{d}\Leftrightarrow ad=bc\) để từ đó rút ra tìm \(x\).
Hướng dẫn
giải chi tiết
\(\begin{array}{l}a)\,\frac{{ – 1}}{2}:(2x – 1) = 0,2:\frac{{ – 3}}{5}\\\,\,\,\,\,\frac{{ – 1}}{2}:\left( {2x – 1} \right) = \frac{1}{5}:\frac{{ – 3}}{5}\\\,\,\,\,\,\,\frac{{ – 1}}{2}:\left( {2x – 1} \right) = \frac{{ – 1}}{3}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,2x – 1 = \frac{{ – 1}}{2}:\frac{{ – 1}}{3}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,2x – 1 = \frac{3}{2}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,2x\,\,\,\,\,\,\,\, = \frac{3}{2} + 1 = \frac{5}{2}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\, = \frac{5}{2}:2\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\, = \frac{5}{4}\end{array}\)
b. \(\frac{16}{x}=\frac{x}{25}\)
\(\begin{align} & {{x}^{2}}=16.25 \\ & {{x}^{2}}=400 \\ \end{align}\)
Suy ra \(x=20\) hoặc \(x=-20\)
Vậy \(x=20\) hoặc \(x=-20\)
c. \(\frac{3}{1-2x}=\frac{-5}{3x-2}\)
\(\begin{align} & 3.(3x-2)=-5.(1-2x) \\ & 9x-6=-5+10x \\ & -6+5=10x-9x \\ & x=-1 \\\end{align}\)
Vậy \(x=-1\)
