puteti sa imi explicati la 1 , va rog

[tex]\dfrac{7^{22}-7^{21}}{7^{25}-7^{24}}=\!\dfrac{7^{21}\cdot (7-1)}{7^{24}\cdot (7-1)} = \!{^{^{^{^{^{^{\displaystyle 7^{21})}}}}}}}\!{\dfrac{7^{21}}{7^{24}}} = \dfrac{1}{7^3} = \dfrac{1}{343}[/tex]
Răspuns:
Explicație pas cu pas:
7^22 - 7^21 = 7^21*(7 - 1) = 6*7^21
7^25 - 7^24 = 7^24*(7 - 1) = 6*7^24
fractia devine
6*7^21/6*7^24 = 1/7^3
___________
1 = 7*a
a = 1/7
1/7^3 = a^3