\(\dfrac{17}{15}.\dfrac{25}{4}+\dfrac{17}{5}.\dfrac{15}{4}\)

\(=\dfrac{85}{12}+\dfrac{51}{4}=\dfrac{119}{6}\)

1 giờ=60 phút

=> 0,35 giờ = 0,35 . 60 = 21 phút

=> 0,6 giờ = 0,6 . 60 = 36 phút

\(=\dfrac{1}{13}+\dfrac{-5}{18}-\dfrac{1}{13}+\dfrac{12}{17}-\dfrac{12}{17}+\dfrac{5}{18}-\dfrac{7}{5}\)

\(=\left(\dfrac{1}{13}-\dfrac{1}{13}\right)+\left(\dfrac{-5}{18}+\dfrac{5}{18}\right)+\left(\dfrac{12}{17}-\dfrac{12}{17}\right)-\dfrac{7}{5}\)

\(=-\dfrac{7}{5}\)

\(\dfrac{5}{6}-\dfrac{2}{9}=\dfrac{45}{54}-\dfrac{12}{54}=\dfrac{33}{54}=\dfrac{11}{18}\)

\(2x\dfrac{5}{18}=\dfrac{2}{1}x\dfrac{5}{18}=\dfrac{5}{9}\)

\(\dfrac{3}{4}:\dfrac{9}{10}=\dfrac{3}{4}x\dfrac{10}{9}=\dfrac{5}{6}\)

\(\dfrac{3}{12}+\dfrac{5}{6}-\dfrac{3}{4}=\dfrac{3}{12}+\dfrac{10}{12}-\dfrac{9}{12}=\dfrac{10}{12}=\dfrac{5}{6}\)

x là dấu nhân nhé

a)

có \(75=5^2.3\), \(150=5^2.3.2\)

=> \(ƯCLN\left(75;150\right)=5^2.3=75\)

B)

\(\dfrac{24}{108}=\dfrac{24:12}{180:12}=\dfrac{2}{9}\)

\(\dfrac{80}{32}=\dfrac{80:16}{32:16}=\dfrac{5}{2}\)

\(\text{1+2-3-4+5+6-7-8+9+...+402-403-404+405+406}\)

\(=406+\left(405-404-403+402\right)+\left(401-400-399+398\right)+...\left(5-4-3+2\right)+1\)

\(=406+0+0+...+0+1\)

\(=407\)

\(\text{bc.(b + c) + ca.(c - a) - ab.(a + b)}\)

\(=\text{(bc.b) + (bc.c) + (ca.c) + [ca.(-a)] + (-ab.a) + (-ab.b)}\)

= \(b^2c+bc^2+c^2a-ca^2-a^2b-ab^2\)

moi cho cau kho vay , em ko bt lm