So sánh:
1) \(\left(-\dfrac{1}{4}\right)^8\) và \(\left(\dfrac{1}{8}\right)^5\)
2) \(31^{11}\) và \(17^{14}\)
3) \(102^7\) và \(9^{13}\)
Nguyễn Thanh Hằng Ribi Nkok Ngok Toshiro Kiyoshi giúp zới
\(1)\)\(\left(-\dfrac{1}{4}\right)^8\) và \(\left(\dfrac{1}{8}\right)^5\)
Vì \(\left(-\dfrac{1}{4}\right)^8=\left(\dfrac{1}{4}\right)^8=\left[\left(\dfrac{1}{2}\right)^2\right]^8=\left(\dfrac{1}{2}\right)^{16}\)
\(\left(\dfrac{1}{8}\right)^5=\left[\left(\dfrac{1}{2}\right)^3\right]^5=\left(\dfrac{1}{2}\right)^{15}\)
Vì \(\left(\dfrac{1}{2}\right)^{16}< \left(\dfrac{1}{2}\right)^{15}\)
\(\Rightarrow\left(-\dfrac{1}{4}\right)^8< \left(\dfrac{1}{8}\right)^5\)
