\(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+....+\frac{1}{20}.\left(1+2+....+20\right)\)

\(=1+\frac{1}{2}\times\frac{2.3}{2}+\frac{1}{3}\times\frac{3.4}{2}+...+\frac{1}{20}\times\frac{20.21}{2}\)

\(=\frac{2}{2}+\frac{3}{2}+\frac{4}{2}+...+\frac{21}{2}\)

\(=\frac{\left(2+21\right).20:2}{2}=\frac{230}{2}=115\)

Số cuối là

\(\frac{1}{10}.\left(1+2+3+...+10\right)\) hay \(\frac{1}{20}.\left(1+2+3+...+20\right)\) ??

(-5/30*(3/10)^3 = (-5/3) * 27/1000 = -5*27/ 3*1000 =-9/200

(9/4)^10/(3/2)^18

=(3^2/2^2)/(3/2)^18

=(3/2)^20:(3/2)^18= 2,25 =9/4

câu còn lại như bạn ngo nguyen thanh cong

k mình nha thanks

có gì sai nhờ mấy bạn sửa dùm

\(\left(-\frac{5}{3}\right)\cdot\left(\frac{3}{10}\right)^3=\left(-\frac{5}{3}\right)\cdot\frac{27}{1000}=\frac{-5\cdot27}{3\cdot1000}=\frac{-1\cdot9}{1\cdot200}=-\frac{9}{200}\)

\(\left(\frac{9}{4}\right)^{10}:\left(\frac{3}{2}\right)^{18}=332525673:147789188=2,25=2\frac{1}{4}\)

\(l-\frac{2}{3}l-12\cdot\left(\frac{1}{2}-\frac{1}{3}\right)^2=\frac{2}{3}-12\cdot\left(\frac{1}{6}\right)^2=\frac{2}{3}-12\cdot\frac{1}{36}=\frac{2}{3}-\left(12\cdot\frac{1}{36}\right)=\frac{2}{3}-\frac{1}{3}=\frac{1}{3}\)