Question

Qual deve ser a taxa de juro composto de uma aplicação para que um capital de R$ 8000 renda R$ 1261,00 em 3 meses?

Answer 1

$C=8000\\J=1261\\M=C+J=8000+1261=9261\\i=taxa\%/100=x/100\\t=3~meses$

$M=C(1+i)^{t}\\9261=8000(1+[x/100])^{3}\\9261/8000=([100+x]/100)^{3}\\9261/8000=[100+x]^{3}/100^{3}\\9261*100^{3}/8000=(100+x)^{3}\\\sqrt[3]{9261*100^{3}/8000}=100+x\\\sqrt[3]{9261}*\sqrt[3]{100^{3}}/\sqrt[3]{8000}=100+x\\21*100/20=100+x\\21*5=100+x\\105=100+x\\105-100=x\\x=5\%~ao~m\^es$