## Tìm x 1) x + 1/4 = 4/3 2) 3/4 + 2/5 x = 29/60 3) 1 3/4 x + 1 1/2 = -4/5 4) 11/12 – (2/5 + x) = 2/3 5) 2 3/4

Question

Tìm x
1) x + 1/4 = 4/3 2) 3/4 + 2/5 x = 29/60 3) 1 3/4 x + 1 1/2 = -4/5
4) 11/12 – (2/5 + x) = 2/3 5) 2 3/4 x = 3 1/7 : 0,01 6) 2x. ( x – 1/7) = 0
7) 3/4 + 1/4 : x = 2/5 8) 3,8 : 2x = 1/4 : 2 2/3 9) 0,25 x : 3 = 5/6 : 0,125
10) 1 1/3 : 0,8 = 2/3 : 0,1 x 11) 3,2 x + (-1,2) x + 2,7 = -4,9 12) |x| – 2,2 = 1,3
13) |x + 3/4|- 1/3 = 0 14) |x + 1/3|- 4 = -1 15) |x – 1,5| + |2,5 – x|= 0
Giải hộ mình mấy bài tìm x

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4 years 2021-02-23T18:10:08+00:00 3 Answers 287 views 0

1. 1) $x+\dfrac14=\dfrac43$

$\Rightarrow x=\dfrac43-\dfrac14=\dfrac{13}{12}$

2) $\dfrac34:\dfrac25.x=\dfrac{29}{60}$

$\Rightarrow \dfrac25.x=\dfrac{29}{60}-\dfrac34=-\dfrac4{15}$

$\Rightarrow x=-\dfrac4{15}.\dfrac52=-\dfrac23$

3) $1\dfrac34.x+1\dfrac12=-\dfrac45$

$\Rightarrow\dfrac74.x+\dfrac32=-\dfrac45$

$\Rightarrow\dfrac74.x=-\dfrac45-\dfrac32=\dfrac{-23}{10}$

$\Rightarrow x=\dfrac{-23}{10}.\dfrac47=-\dfrac{-46}{35}$

4) $\dfrac{11}{12}-(\dfrac25+x)=\dfrac23$

$\Rightarrow \dfrac25+x=\dfrac{11}{12}-\dfrac23=\dfrac14$

$\Rightarrow x=\dfrac14-\dfrac25=-\dfrac3{20}$

5) $2\dfrac34.x=3\dfrac17:0,01$

$\Rightarrow\dfrac{11}{4}.x=\dfrac{11}7:\dfrac1{100}=\dfrac{1100}7$

$\Rightarrow x=\dfrac{1100}7.\dfrac4{11}=\dfrac{44}7$

6) $2x.(x-\dfrac17)=0$

$\Rightarrow x-\dfrac17=0$ (1) hoặc $x=0$

(1) $\Rightarrow x=\dfrac17$

Vậy $x=\{0;\dfrac17\}$

7) $\dfrac34+\dfrac14:x=\dfrac25$

$\Rightarrow\dfrac14:x=\dfrac25-\dfrac34=\dfrac{-7}{20}$

$\Rightarrow x=\dfrac14:\dfrac{-7}{20}=\dfrac14.\dfrac{-20}{7}=-\dfrac57$

8) $3,8:2x=\dfrac14:2\dfrac23$

$\Rightarrow 1,9x=\dfrac14:\dfrac83=\dfrac14.\dfrac38=\dfrac3{32}$

$\Rightarrow x=\dfrac3{32}:1,9=\dfrac{15}{304}$

9) $0,25x:3=\dfrac56:0,125=\dfrac56:\dfrac18=\dfrac56.8=\dfrac{20}3$

$\Rightarrow 0,25x=\dfrac{20}3.3=20$

$\Rightarrow x=20:0,25=80$

10) $1\dfrac13:0,8=\dfrac23:0,1x$

$\Rightarrow \dfrac43:\dfrac45=\dfrac23:\dfrac1{10}.x$

$\Rightarrow \dfrac53=\dfrac{20}3.x$

$\Rightarrow x=\dfrac53:\dfrac{20}3=\dfrac14$

11) $3,2x+(-1,2)x+2,7=-4,9$

$\Rightarrow 2x+2,7=-4,9$

$\Rightarrow 2x=-4,9-2,7=-7,6$

$\Rightarrow x=-3,8$

12) $|x|-2,2=1,3$

$\Rightarrow|x|=1,3+2,2=3,5$

$\Rightarrow x=\pm3,5$

13) $|x+\dfrac34|-\dfrac13=0$

$\Rightarrow|x+\dfrac34|=\dfrac13$

$\Rightarrow x+\dfrac34=\dfrac13\Rightarrow x=-\dfrac5{12}$

hoặc $x+\dfrac34=-\dfrac13\Rightarrow x=-\dfrac{13}{12}$

Vậy $x=\{-\dfrac5{12};-\dfrac{13}{12}\}$

14) $|x+\dfrac13|-4=-1$

$\Rightarrow|x+\dfrac13|=-1+4=3$

$\Rightarrow x+\dfrac13=3\Rightarrow x=\dfrac83$

Hoặc $x+\dfrac13=-3\Rightarrow x=-3-\dfrac13=-\dfrac{10}3$

15) Do $|x-1,5|\ge0$ và $|2,5-x|\ge0$ với mọi giá trị của $x$

$\Rightarrow |x-1,5|+|2,5-x|=0$ khi

$\Rightarrow x-1,5=0\Rightarrow x=1,5$ và $2,5-x=0\Rightarrow x=2,5$ (loại vì ra 2 kết quả khác nhau)

2. Bạn xem hình

$14) \left | x+\frac{1}{3} \right |-4=-1\\\Leftrightarrow \left | x+\frac{1}{3} \right |=-1+4=3\\\Leftrightarrow \left[ \begin{array}{l}x+\frac{1}{3}=3\\x+\frac{1}{3}=-3\end{array} \right.\\\Leftrightarrow \left[ \begin{array}{l}x=\frac{8}{3}\\x=-\frac{10}{3}\end{array} \right.$
Vậy $x\in \left \{ \frac{8}{3};\frac{-10}{3} \right \}$
$15) \left | x-1,5 \right |+\left | 2,5-x \right |=0\\\Leftrightarrow \left | x-1,5 \right |=-\left | 2,5-x \right |\\\Leftrightarrow \left[ \begin{array}{l}\left | x-1,5 \right |=0\\-\left |2,5-x \right |=0\end{array} \right.\\\Leftrightarrow \left[ \begin{array}{l}x=1,5\\x=2,5\end{array} \right.\\\Rightarrow x\in \varnothing$
Vậy $x\in \varnothing$

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