a, x – `1/4` = `2/3` . `9/8` b, `3/x` = `y/28` = `-39/91` c, `-2/9` – x = `-5/36` d, `5/x` = `-15/-6`

0 bình luận về “a, x – `1/4` = `2/3` . `9/8` b, `3/x` = `y/28` = `-39/91` c, `-2/9` – x = `-5/36` d, `5/x` = `-15/-6`”

1. Đáp án:

   `a)`

   `x-1/4=2/3 . 9/8`

   `=> x-1/4=3/4`

   `=> x=3/4+1/4=1`

   Vậy `x=1`

   `b)`

   `3/x=y/28=-39/91`

   `=> 3/x=y/28=-3/7`

   `+) 3/x=-3/7 => -3x=-21 => x=7`

   `+) y/28=-3/7 => -7y=84 => y=-12`

   Vậy `(x;y)=(7;12)`

   `c)`

   `-2/9-x=-5/36`

   `=> x=(-2/9)-(-5/36)`

   `=> x=-1/12`

   Vậy `x=-1/12`

   `d) 5/x=(-15)/(-6)`

   `=> -15x=-30`

   `=> x=2`

   Vậy `x=2`

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2. a. x -$\frac{1}{4}$ = $\frac{2}{3}$ . $\frac{9}{8}$ 

       X- $\frac{1}{4}$ = $\frac{3}{4}$ 

                             X= $\frac{3}{4}$ + $\frac{1}{4}$ 

                               x= 1

   B. $\frac{3}{x}$ = $\frac{y}{28}$ = -$\frac{39}{91}$  

       $\frac{3}{x}$ = $\frac{y}{28}$ = -$\frac{3}{7}$ 

   ⇒$\frac{3}{x}$ = -$\frac{3}{7}$ ⇒ -3x=21 ⇒ x=-7

   ⇒$\frac{y}{28}$ = -$\frac{3}{7}$ ⇒ 7y=-84 ⇒ y=-12

   C. -$\frac{2}{9}$ – x = -$\frac{5}{36}$  

         ⇒ x= -$\frac{2}{9}$ + $\frac{5}{36}$ 

       ⇒ x = -$\frac{1}{2}$ 

   D. $\frac{5}{x}$ = -$\frac{15}{-6}$ ⇒ $\frac{5}{x}$  = $\frac{5}{2}$  ⇒ x=2

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