a: =-2/49-5/3+2/49=-5/3

b: \(=\dfrac{5\cdot4^{15}\cdot9^9-4\cdot3^{20}\cdot8^9}{5\cdot2^9\cdot6^{19}-7\cdot2^{29}\cdot27^6}\)

\(=\dfrac{5\cdot2^{30}\cdot3^{18}-3^{20}\cdot2^{27}\cdot2^2}{5\cdot2^9\cdot2^{19}\cdot3^{19}-7\cdot2^{29}\cdot3^{18}}\)

\(=\dfrac{5\cdot2^{30}\cdot3^{18}-3^{20}\cdot2^{29}}{5\cdot2^{28}\cdot3^{19}-7\cdot2^{29}\cdot3^{18}}\)

\(=\dfrac{2^{29}\cdot3^{18}\left(2\cdot3-3^2\right)}{2^{28}\cdot3^{18}\left(5\cdot3-7\cdot2\right)}=2\cdot\dfrac{6-9}{15-14}=2\cdot\left(-3\right)=-6\)

Bạn ghi lại đề đi bạn bằng công thức latex á

:v cái này bn lên mạng ý

\(A=5\cdot4^{15}\cdot9^9-4\cdot3^{20}\cdot8^9\)

\(A=5\cdot\left(2^2\right)^{15}\cdot\left(3^2\right)^9-2^2\cdot3^{20}\cdot\left(2^3\right)^9\)

\(A=5\cdot2^{30}\cdot3^{18}-2^2\cdot3^{20}\cdot2^{27}\)

\(A=5\cdot2^{30}\cdot3^{18}-2^{29}\cdot3^{20}\)

\(A=2^{29}\cdot3^{18}\cdot\left(5\cdot2^1\cdot1-1\cdot3^2\right)\)

\(A=2^{29}\cdot3^{18}\cdot\left(5-9\right)\)

\(A=-2^2\cdot2^{29}\cdot3^{18}\)

\(A=-2^{31}\cdot3^{18}\)

_______________

\(B=5\cdot2^9\cdot6^{19}-7\cdot2^{29}\cdot27^6\)

\(B=5\cdot2^9\cdot2^{19}\cdot3^{19}-7\cdot2^{29}\cdot\left(3^3\right)^6\)

\(B=5\cdot2^{28}\cdot3^{19}-7\cdot2^{29}\cdot3^{18}\)

\(B=2^{28}\cdot3^{18}\cdot\left(5\cdot1\cdot3-7\cdot2\cdot1\right)\)

\(B=2^{28}\cdot3^{18}\cdot\left(15-14\right)\)

\(B=2^{28}\cdot3^{18}\)

Ta có: \(A:B\)

\(=\left(-2^{31}\cdot3^{18}\right):\left(2^{28}\cdot3^{18}\right)\)

\(=\left(-2^{31}:2^{28}\right)\cdot\left(3^{18}:3^{18}\right)\)

\(=-2^3\cdot1\)

\(=-8\)

100%