Question

Tính giá trị của biểu thức sau:

a) \(\dfrac{2^8.9^2}{6^4.8^2}\) b) \(\left(2^{-1}+3^{-1}\right):\left(2^{-1}-3^{-1}\right)+\left(2^{-1}.2^0\right).2^3\)

Answer 1

a) Có \(\dfrac{2^8.9^2}{6^4.8^2}\)=\(\dfrac{2^8.3^4}{3^4.2^42^6}\)=\(\dfrac{2^8.3^4}{3^4.2^{10}}\)=\(\dfrac{2^8}{2^{10}}\)=\(\dfrac{1}{4}\)

b) Có \(\left(2^{-1}+3^{-1}\right):\left(2^{-1}-3^{-1}\right)+\left(2^{-1}.2^0\right).2^3\)

= \(\dfrac{2^{-1}+3^{-1}}{2^{-1}-3^{-1}}+2^{-1}.2^3\)

=\(\dfrac{\dfrac{1}{2}+\dfrac{1}{3}}{\dfrac{1}{2}-\dfrac{1}{3}}+\dfrac{1}{2}.2^3\)

= \(\dfrac{\dfrac{5}{6}}{\dfrac{1}{6}}+2^2\)=5+8=13