\(=\dfrac{8}{15}-\dfrac{1}{16}:\dfrac{9}{8}\)

\(=\dfrac{8}{15}-\dfrac{1}{18}\)

\(=\dfrac{43}{90}\)

Kéo dài AC cắt Dy tại E ta có

\(\widehat{DEC}=\widehat{CAx}=50^o\) (góc so le trong)

\(\widehat{DCE}=\widehat{ACE}-\widehat{ACD}=180^o-110^o=70^o\)

Xét tg DCE có

\(\widehat{CDy}=180^o-\widehat{DEC}-\widehat{DCE}=180^o-50^o-70^o=60^o\) (trong tg tổng các góc trong bằng 180 độ)

Ta có: V=S.h

=> 50=S.5

=> S=50:5=10  cm

\(\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{10}...+\dfrac{2}{x\left(x+1\right)}=\dfrac{2017}{2019}\)

\(\Rightarrow\dfrac{2}{6}+\dfrac{2}{12}+...+\dfrac{2}{x\left(x+1\right)}=\dfrac{2017}{2019}\)

\(\Rightarrow2.\left(\dfrac{1}{2}-\dfrac{1}{x+1}\right)=\dfrac{2017}{2019}\)

\(\Rightarrow\dfrac{1}{2}-\dfrac{1}{x+1}=\dfrac{2017}{4038}\)

\(\Rightarrow\dfrac{1}{x+1}=\dfrac{1}{2019}\)

\(x=2018\)

a, 25/4 

b, 51/5

6 giờ 15 phút = 6,4 giờ

10 giờ 12 phút = 10,5 giờ

\(A=3-\left(-\dfrac{6}{7}\right)^0+\left(\dfrac{1}{2}\right)^2:2+\dfrac{1}{8}:\left(\dfrac{1}{2}\right)^5\\ =3-1+\dfrac{1}{4}.\dfrac{1}{2}+\dfrac{1}{8}:\dfrac{1}{32}\\ =2+\dfrac{1}{8}+\dfrac{1}{8}.32\\ =2+\dfrac{1}{8}.33=2+\dfrac{33}{8}=\dfrac{49}{8}\)

(-0,125)⁸>(0,25)²⁴, 4¹⁰⁰=2²⁰⁰

^{chúc bạn học tốt nhé}