c)
Scoatem factor comun la numarator si numitor pe 5^n * 7^n si avem:
[tex] \frac{5^{n}*7^{n}(5^{2}+7)}{5^{n}*7^{n}(5*7+5^{2})}= \frac{25+7}{35+25} = \frac{32}{60}= \frac{8}{15} [/tex]
d)
Scoatem factor comun la numitor si numarator 5^n.
[tex] \frac{5^{n}(1+5+5^{2}+5^{3})}{5^{n}(5+5^{3})} = \frac{1+5+25+125}{5+125}= \frac{156}{130}= \frac{78}{65} [/tex]
