Question

A = \(\frac{a^5+a^6+a^7+a^8}{a^{-5}+a^{-6}+a^{-7}+a^{-8}}\)

Tinh bieu thuc A tai a=2015

Answer 1

Ta có:

\(\frac{a^5+a^6+a^7+a^8}{a^{-5}+a^{-6}+a^{-7}+a^{-8}}\)

\(=\frac{a^5+a^6+a^7+a^8}{\frac{1}{a^5}+\frac{1}{a^6}+\frac{1}{a^7}+\frac{1}{a^8}}\)

\(=a^{5+6+7+8}=a^{26}\)

Thay vào sẽ là:

\(2015^{26}=8.149881843.10^{85}\)

Answer 2

\(A=\frac{a^3\left(a^3+a^2+a+1\right).a^8}{a^3+a^2+a^1+a}=a^{24}\)

Answer 3

A = ( a⁵ + a⁶ + a⁷ + a⁸ )²