Giúp me:<. Hứa vote 5 seo

Các bước giải:

Câu 1:

a)$\frac{1}{7}$ + $\frac{-2}{11}$ + $\frac{6}{7}$ 

 =($\frac{1}{7}$ + $\frac{6}{7}$ ) + $\frac{-2}{11}$ 

 =  1 + $\frac{-2}{11}$ 

 = $\frac{9}{11}$ 

b)$\frac{7}{23}$ + $\frac{4}{17}$ - $\frac{7}{23}$ + $\frac{13}{17}$  

=$\frac{7}{23}$ - $\frac{7}{23}$ + $\frac{4}{17}$ + $\frac{13}{17}$ 

= 0 + 1

= 1

c) $\frac{3}{7}$ / $\frac{5}{3}$ + $\frac{3}{7}$ / $\frac{5}{4}$ - 1$\frac{3}{5}$ 

=$\frac{3}{7}$ * $\frac{3}{5}$ + $\frac{3}{7}$ * $\frac{4}{5}$ - $\frac{8}{5}$ 

=$\frac{3}{7}$ * ( $\frac{3}{5}$ + $\frac{4}{5}$ ) - $\frac{8}{5}$ 

=$\frac{3}{7}$ * $\frac{7}{5}$ - $\frac{8}{5}$ 

=$\frac{3}{5}$ - $\frac{8}{5}$

=-1

Câu 2:

a)

$\frac{7}{8}$ + x = $\frac{3}{5}$ 

x= $\frac{3}{5}$ - $\frac{7}{8}$

x=-$\frac{11}{4}$ 

b)

$\frac{1}{2}$x - $\frac{2}{5}$ = $\frac{1}{5}$ 

$\frac{1}{2}$x = $\frac{1}{5}$ + $\frac{2}{5}$ 

$\frac{1}{2}$x = $\frac{3}{5}$ 

x = $\frac{3}{5}$ / $\frac{1}{2}$ 

x = $\frac{6}{5}$ 

c)

|x|=$\frac{3}{4}$ nếu x < 0

⇒ x = ±$\frac{3}{4}$ 

Mà x < 0

⇒ x = -$\frac{3}{4}$ 

d)

|x+1|=2

⇒x+1 = ±2

Nếu x+1 = 2

        x     = 2-1

        x     = 1

Nếu x+1 = -2

        x    = (-2) -1

        x    = -3