\(\left(\dfrac{1}{4}+\dfrac{-5}{13}\right)+\left(\dfrac{2}{11}+\dfrac{-8}{13}+\dfrac{3}{4}\right)\)

\(=\dfrac{1}{4}+\dfrac{-5}{13}+\dfrac{2}{11}+\dfrac{-8}{13}+\dfrac{3}{4}\)

\(=\left(\dfrac{1}{4}+\dfrac{3}{4}\right)+\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\dfrac{2}{11}\)

\(=1+\left(-1\right)+\dfrac{2}{11}\)

\(=0+\dfrac{2}{11}\)

\(=\dfrac{2}{11}\)

=))

phép tính hơi tắt ạ

\(\dfrac{45}{19}-\left[\dfrac{1}{2}+\left(\dfrac{1}{3}+\left(\dfrac{1}{4}\right)^{-1}\right)^{-1}\right]^{-1}\)

\(=\dfrac{45}{19}-\left[\dfrac{1}{2}+\left(\dfrac{1}{3}+4\right)^{-1}\right]^{-1}\)

\(=\dfrac{45}{19}-\left[\dfrac{1}{2}+\left(\dfrac{13}{3}\right)^{-1}\right]^{-1}\)

\(=\dfrac{45}{19}-\left[\dfrac{1}{2}+\dfrac{3}{13}\right]^{-1}\)

\(=\dfrac{45}{19}-\left[\dfrac{13}{26}+\dfrac{6}{26}\right]^{-1}\)

\(=\dfrac{45}{19}-\left[\dfrac{19}{26}\right]^{-1}\)

\(=\dfrac{45}{19}-\dfrac{26}{19}\)

\(=1\)

\(\dfrac{4}{9}+\left(\dfrac{2}{9}+\dfrac{5}{70}\right)\)

\(=\dfrac{4}{9}+\left(\dfrac{2}{9}+\dfrac{1}{14}\right)\)

\(=\dfrac{4}{9}+\left(\dfrac{28}{126}+\dfrac{9}{126}\right)\)

\(=\dfrac{4}{9}+\dfrac{37}{126}\)

\(=\dfrac{56}{126}+\dfrac{37}{126}\)

\(=\dfrac{31}{42}\)

Độ dài 1 cạnh của hình lập phương là : \(20,8:4=5,2\left(cm\right)\)

Diện tích xung quanh hình lập phương là : \(5,2\times5,2\times4=108,16\left(cm^2\right)\)

Diện tích toàn phần hình lập phương là : \(5,2\times5,2\times5,2=140,608\left(cm^2\right)\)

\(\dfrac{5}{7}+\dfrac{3}{18}=\dfrac{90}{126}+\dfrac{21}{126}=\dfrac{37}{42}\)

\(\dfrac{15}{24}+\dfrac{12}{16}=\dfrac{240}{384}+\dfrac{288}{384}=\dfrac{11}{8}\)

\(\dfrac{5}{6}+\dfrac{3}{4}=\dfrac{20}{24}+\dfrac{18}{24}=\dfrac{19}{12}\)

\(\dfrac{3}{8}+\dfrac{7}{12}=\dfrac{36}{96}+\dfrac{56}{96}=\dfrac{23}{24}\)

xem lại bài nhé