指數題目：2.5^a = 1000, 0.25^b = 1000，求 (b-a) / ab.
[quote]2.5^a = 1000 and 0.25^b = 1000求 (b-a) / ab = 1/3[/quote]
2.5^a = 10^3 and 0.25^b = 10^3
→ 2.5 = 10^{3/a}, 0.25 = 10^{3/b}
兩式相除
→ 2.5 / 0.25 = 10^{3/a - 3/b}
→ 10 = 10^{3/a - 3/b}
→ 1 = 3/a - 3/b
→ 1/a - 1/b = 1/3
→ (b-a)/ab = 1/3
頁:
[1]