Question #5bb0e

2 Answers
Sep 20, 2017

k=2

Explanation:

in more detail:
5^(k+1)=x5k+1=x
(5 * x) + x - 750 = 0(5x)+x750=0
6 * x = 750 6x=750
->x=125 x=125
5^(k+1)=1255k+1=125
->k=2k=2

Oct 31, 2017

Taking to where you can take over

Explanation:

Just to make things a bit more strait forward:

Set m=k-1m=k1 then we have:

5^(m+3)+5^m=7505m+3+5m=750

5^m(5^3+1)=7505m(53+1)=750

5^m=750/1265m=750126

taking logs

mln(5)=ln(750)-ln(126)mln(5)=ln(750)ln(126)

m= (ln(750)-ln(126))/ln(5) m=ln(750)ln(126)ln(5)

Thus k-1= (ln(750)-ln(126))/ln(5)k1=ln(750)ln(126)ln(5)

I will let you do the rest.