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) $0,5.(-0,75)+1,25.(-0,5)$
$=(-0,5).0,75+1,25.(-0,5)$
$=-0,5.(1,25+0,75)$
$=-0,5.2=-1$
