Giải thích các bước giải:

Câu 2:

   ( 1 - 2x  )³ = -8

⇔( 1 - 2x )³ = ( -2 )³

⇔ 1 - 2x = -2

⇔ -2x = -3

⇔ x = $\frac{3}{2}$ 

Câu 1:

$\dfrac{3}{4}.5\dfrac{3}{15}-0,75.\dfrac{36}{13}$

$=\dfrac{3}{4}.\dfrac{78}{15}-\dfrac{3}{4}.\dfrac{36}{13}$

$=\dfrac{3}{4}.(\dfrac{78}{15}-\dfrac{36}{13})$

$=\dfrac{3}{4}.\dfrac{158}{65}=\dfrac{237}{130}$

Câu 2: 

$(1-2x)^3=-8=-2^3$

$⇒1-2x=-2$

$⇒2x=3$

$⇒x=\dfrac{3}{2}$

Câu 3:

`(\frac{8}{27})^n=(\frac{2}{3})^12`

`(\frac{8}{27})^n=(\frac{8}{27})^4`

$⇒n=4$

Câu 4:

a) $-\dfrac{3}{8}.16\dfrac{8}{7}-0,375.7\dfrac{9}{17}$

$=\dfrac{3}{8}.-\dfrac{120}{7}-\dfrac{3}{8}.\dfrac{128}{7}$

$=\dfrac{3}{8}.(-\dfrac{120}{7}-\dfrac{128}{7})$

$=\dfrac{3}{8}.\dfrac{-248}{7}=-\dfrac{93}{7}$

b) $0,5.(-0,75)+1,25.(-0,5)$

$=(-0,5).0,75+1,25.(-0,5)$

$=-0,5.(1,25+0,75)$

$=-0,5.2=-1$