Đáp án:
Giải thích các bước giải:
7.9-14 / 3-17
$=\frac{7. 9- 7.2}{-14}$
$= \frac{7. (9- 2)}{-14}$
$= \frac{7. 7}{-14}$
$= \frac{49}{-14}$
$= \frac{-7}{2}$ (đổi dấu)
`25\%-3/2+0,5.12/5.2\5%-1`
$= \frac{1}{4}- \frac{3}{2}+ \frac{1}{2}. \frac{12}{5}. \frac{1}{4}- 1$
$= \frac{1}{4}- \frac{3}{2}+ \frac{3}{10}- 1$
$= \frac{5}{20}- \frac{30}{20}+ \frac{6}{20}$
$= \frac{5- 30+ 6}{20}= \frac{-21}{20}$
Tìm `x`
`( 14/5x + 50 ) :2/3 = -51`
$\frac{14}{5}x+ 50= -51. \frac{2}{3}$
$\frac{14}{5}x+ 50= -34$
$\frac{14}{5}x = -34- 50$
$\frac{14}{5}x= -84$
$x= -84: \frac{14}{5}$
$x= -30$
`8x-0,4 = 7,8x + 402`
$8x- 7,8. x= 402+ 0,4$
$0, 2. x= 402,04$
$x= 402,04: 2$
$x= 2012$
