Guthaben nach 1 Jahr: G(1)= 1900*1,045
" 2 " : G(2)=(1900*1,045+1900)*1,045 = 1900*1,0452+1900*1,045=1900*(1,0452+1,045)
" 12 " : G(12)=1900*(1,04512+1,04511+1,04510+ ... +1,045)=1900*1,045(1,04511+1,04510+ ... +1)
=1900*1,045*\( \frac{1-1,045^{12}}{1-1,045} \) =27481,66, weil
1+q+q2+q3+qn = \( \frac{1-q^{n+1}}{1-q} \), q≠1,n∈ℕ