Question

Tìm x

A, | 2x - 1 | = | x + 3 |

B, ( 2x + 5 )^10 < ( x + 7 )^10

C, | x - 5 | < 4

D, | x + 7 | > 3

Answer 1

|2x-1|=|x+3|

=> 2x-1=x+3 =>x=4

Hoặc 2x-1=-x-3 => x=-2/3

Vậy x thuộc { 4; -2/3}

Answer 2

A) \(\left|2x-1\right|=\left|x+3\right|\)

\(\Rightarrow\left[{}\begin{matrix}2x-1=x+3\\1-2x=x+3\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}2x-x=3+1\\-2x-x=3-1\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=4\\-3x=2\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=4\\x=-\dfrac{2}{3}\end{matrix}\right.\)

Vậy \(\left[{}\begin{matrix}x=4\\x=-\dfrac{2}{3}\end{matrix}\right.\)

Answer 3

câu B

| 2x +5| < |x+7|

TH1

khi x<-7

-2x-5 <-x-7

-x<-7+5 =-2

=> x>2 => loại đang xét x<-7

TH2

khi -7<=x<-5/2

-2x-5 <x+7

-3x<+7+5 =12

-3x<12 => x>-12/3 =>-12/3 <x <-5/2

TH3 x>=-5/2

2x+5<x+7

x<7-5 =2 => x<2

=> -5/2<=x<2

kl

-4<x<2