1: \(\dfrac{x}{-4}=\dfrac{2}{5}\)
=>\(x=-4\cdot\dfrac{2}{5}=-\dfrac{8}{5}\)
2: \(\dfrac{5}{6}=\dfrac{x}{4}\)
=>\(x=\dfrac{5\cdot4}{6}=\dfrac{20}{6}=\dfrac{10}{3}\)
3: \(\dfrac{x}{1,5}=\dfrac{-4}{3}\)
=>\(x=\dfrac{-4\cdot1,5}{3}=-\dfrac{6}{3}=-2\)
28: \(\dfrac{7-2x}{-3}=\dfrac{8-3x}{-4}\)
=>\(\dfrac{2x-7}{3}=\dfrac{3x-8}{4}\)
=>\(3\left(3x-8\right)=4\left(2x-7\right)\)
=>9x-24=8x-28
=>9x-8x=-28+24
=>x=-4
29: ĐKXĐ: \(x\notin\left\{3;-5\right\}\)
\(\dfrac{-15}{3-x}=\dfrac{12}{x+5}\)
=>\(\dfrac{15}{x-3}=\dfrac{12}{x+5}\)
=>\(\dfrac{5}{x-3}=\dfrac{4}{x+5}\)
=>5(x+5)=4(x-3)
=>5x+15=4x-12
=>5x-4x=-12-15
=>x=-27(nhận)
\(1,\dfrac{x}{-4}=\dfrac{2}{5}\)
\(x.5=2.\left(-4\right)\)
\(x.5=-8\)
\(x=\dfrac{-8}{5}\)
\(2,\dfrac{5}{6}=\dfrac{x}{4}\)
\(5.4=x.6\)
\(20=x.6\)
\(20:6=x\)
\(\dfrac{10}{3}=x\)
\(28,\dfrac{7-2x}{-3}=\dfrac{8-3x}{-4}\)
\(\left(7-2x\right).\left(-4\right)=\left(8-3x\right).\left(-3\right)\)
\(28-8x=24-9x\)
\(9x-8x=24-28\)
\(x=-4\)
