Câu hỏi của Nguyễn Thùy Chi

Question

a,$\left|3x+4\right|=2\left|2x-9\right|$

b,$\left|10x+7\right|< 37$

c,$\left|3-8x\right|\le19$

d,$\left|x+3\right|-2x=\left|x-4\right|$

tìm x giúp mk

Mashiro Shiina · Accepted Answer

$\left|3x+4\right|=2\left|2x-9\right|$

$\left|3x+4\right|\ge0$

$\left|2x-9\right|\ge0\Rightarrow2\left|2x-9\right|\ge0$

$\Rightarrow3x+4=2\left(2x-9\right)$

$3x+4=4x-18$

$3x=4x-14$

$x=14$

$\left|10x+7\right|\le37$

$\Rightarrow\left|10x+7\right|\le\left\{37;36;35;......;0\right\}$

$10x+7\le\left\{\pm37;\pm36;\pm35;.....0\right\}$

Tự tính tiếp.C tương tự

$\left|x+3\right|-2x=\left|x-4\right|$

$\left|x+3\right|=\left|x-4\right|+2x$

$\left|x+3\right|\ge0$

$\left|x-4\right|\ge0$

$\Rightarrow x+3=x-4+2x$

$x+3=3x-4$

$x=3x-7$

$x=\dfrac{7}{2}$Câu trả lời: $\left|3x+4\right|=2\left|2x-9\right|$