Đáp án:
Giải thích các bước giải:
$1)\dfrac{17.5-17}{3-20}=\dfrac{17(5-1)}{-17}=-(5-1)=-4$
$2)\dfrac{4.5+11.4}{8.7+4.3}=\dfrac{4.(11+5)}{4.(14+3)}=\dfrac{4.16}{4.17}=\dfrac{16}{17}$
$3.\dfrac{1919+101}{2.2929+404}$
$=\dfrac{2020}{5858+404}=\dfrac{2020}{6262}$
$=\dfrac{10}{31}$
$4.\dfrac{-15.8+10.7}{5.6+20.3}$
$=\dfrac{5.(-3).8+5.2.7}{5.6+5.4.3}$
$=\dfrac{5(-24+14)}{5(6+12)}$
$=\dfrac{5.(-10)}{5.18}$
$=\dfrac{-10}{-18}$
$=\dfrac{5}{9}$
