Question

|5x+3|+|2x+1|=|7x+4|

Answer 1

5х+3+2х+1=7х+4

5х+2х-7х=4-3-1

Ответ:0 

Answer 2

5х+3=0    х = -3/5

2х+1=0    х = -1/2

7x+4=0    x =  -4/7

-,-,-    +;-;-    +;-;+     +;+;+ 

------'--------'----------'------->

      -3/5    -4/7     -1/2

Раскроем знак модуля на каждом из интервалов:

1) $left { {{x(-infty;-3/5)} atop {-5x-3-2x-1=-7x-4}} right.$ 

-7x-4=-7x-4

0=0

 2) $left { {{x[-3/5;-4/7]} atop {5x+3-2x-1=-7x-4}} right.$

10x = -6

x = -0.6

3) $left { {{x(-4/7;-1/2]} atop {5x+3-2x-1=7x+4}} right.$ 

-4x=2

x = -0.5

4) $left { {{x(-1/2;+infty)} atop {5x+3+2x+1=7x+4}} right.$ 

7x+4=7x+4

0=0

Ответ: х = -0,6. х = -0,5