Question

Tính giá trị của các biểu thức sau:

a) \(\frac{45^{10}.5^{20}}{75^{15}}\);                                         b) \(\frac{\left(0,8\right)^5}{\left(0,4\right)^6}\);                       c) \(\frac{2^{15}.9^4}{6^6.8^3}\)

Answer 1

a) \(\frac{45^{10}.5^{20}}{75^{15}}=\frac{\left(3^2.5\right)^{10}.5^{20}}{\left(3.5^2\right)^{15}}=\frac{3^{20}.5^{10}5^{20}}{3^{15}.5^{30}}=\frac{3^{20}.5^{30}}{3^{15}.5^{30}}=3^5=243\)

b) \(\frac{\left(0,8\right)^5}{\left(0,4\right)^6}=\left(0,8\right)^5:\left(0,4\right)^6=\left(\frac{4}{5}\right)^5:\left(\frac{2}{5}\right)^6=\frac{4^5}{5^5}:\frac{2^6}{5^6}=\frac{4^5}{5^5}.\frac{5^6}{2^6}=\frac{2^{10}}{5^5}.\frac{5^6}{2^6}=2^4.5=16.5=80\)

c) \(\frac{2^{15}.9^4}{6^6.8^3}=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^6.\left(2^3\right)^3}=\frac{2^{15}.3^8}{2^6.3^6.2^9}=\frac{2^{15}.3^8}{2^{15}.3^6}=3^2=9\)