4.318 Найдите х из пропорции: a) x/-1,4 = -7,3/-2,8; б) -8,4/105 = -12,6/x ; в) -2,5x/14 = 1/(-30); г) -7 1/2 : 4 1/2 = x/3/25

Ответ: a) x = 3.65; б) x = 157.5; в) x = 7/375; г) x = -25/3

1. a) \[\frac{x}{-1.4} = \frac{-7.3}{-2.8}\] \[x = \frac{-1.4 \cdot (-7.3)}{-2.8}\] \[x = \frac{1.4 \cdot 7.3}{2.8}\] \[x = \frac{10.22}{2.8}\] \[x = 3.65\]
2. б) \[\frac{-8.4}{105} = \frac{-12.6}{x}\] \[x = \frac{105 \cdot (-12.6)}{-8.4}\] \[x = \frac{105 \cdot 12.6}{8.4}\] \[x = \frac{1323}{8.4}\] \[x = 157.5\]
3. в) \[\frac{-2.5x}{14} = \frac{1}{-30}\] \[-2.5x = \frac{14}{-30}\] \[x = \frac{14}{-30 \cdot (-2.5)}\] \[x = \frac{14}{75}\] \[x = \frac{7}{37.5} = \frac{1}{375} \approx 0.186666667\]
4. г) \[\frac{-7\frac{1}{2}}{4\frac{1}{2}} = \frac{x}{\frac{3}{25}}\] \[\frac{-\frac{15}{2}}{\frac{9}{2}} = \frac{x}{\frac{3}{25}}\] \[x = \frac{-\frac{15}{2} \cdot \frac{3}{25}}{\frac{9}{2}}\] \[x = \frac{-\frac{45}{50}}{\frac{9}{2}}\] \[x = -\frac{45}{50} \cdot \frac{2}{9}\] \[x = -\frac{90}{450}\] \[x = -\frac{1}{5}\]

Ответ: a) x = 3.65; б) x = 157.5; в) x = 7/375; г) x = -25/3