So sánh (–5)39 và (–2)91.
So sánh (–5)39 và (–2)91.
Ta có:
(–5)39 = [(–5)3]13 = (–125)13
(–2)91 = [(–2)7]13 = (–128)13
Vì (–125)13 > (–128)13 nên (–5)39 > (–2)91.