Question

So sánh hai phân số : \(\left(-\dfrac{1}{5}\right)^{30}\)và \(\left(-\dfrac{1}{3}\right)^{50}\)

Answer 1

Ta có: \(\left(-\dfrac{1}{5}\right)^{30}=\left[\left(-\dfrac{1}{5}\right)^3\right]^{10}=\left(-\dfrac{1}{125}\right)^{10}\\ \left(-\dfrac{1}{3}\right)^{50}=\left[\left(-\dfrac{1}{3}\right)^5\right]^{10}=\left(-\dfrac{1}{243}\right)^{10}\\ Vì:\left(-\dfrac{1}{125}\right)^{10}< \left(-\dfrac{1}{243}\right)^{10}\left(do:-\dfrac{1}{125}< -\dfrac{1}{243}\right)\\ =>\left(-\dfrac{1}{5}\right)^{30}< \left(-\dfrac{1}{3}\right)^{50}\left(đpcm\right)\)