Câu 8:
\(D=\dfrac{21^2\cdot14\cdot126}{35^5\cdot6}\)
\(=\dfrac{7^2\cdot3^2\cdot2\cdot7\cdot7\cdot2\cdot3^2}{5^5\cdot7^5\cdot2\cdot3}\)
\(=\dfrac{7^4\cdot3^4\cdot2^2}{5^5\cdot7^5\cdot2\cdot3}=\dfrac{3^3\cdot2}{7\cdot5^5}\)
Câu 10:
\(\dfrac{2^3\cdot9^4+9^3\cdot45}{9^2\cdot10+9^2\cdot3}\)
\(=\dfrac{2^3\cdot9^4+9^4\cdot5}{9^2\cdot13}\)
\(=\dfrac{9^4\left(8+5\right)}{9^2\cdot13}=9^2=81\)
Câu 11:
\(A=\dfrac{3^{10}\cdot10+3^{10}\cdot6}{3^6\cdot2^{2^2}}\)
\(=\dfrac{3^{10}\cdot16}{3^6\cdot2^4}=3^4=81\)
Câu 12:
\(B=\dfrac{11\cdot3^{22}\cdot3^7-9^{15}}{\left(2\cdot3^{14}\right)^2}\)
\(=\dfrac{11\cdot3^{29}-3^{30}}{2^2\cdot3^{28}}\)
\(=\dfrac{3^{29}\left(11-3\right)}{2^2\cdot3^{28}}=\dfrac{3\cdot8}{4}=3\cdot2=6\)
