Question

Calcule o 1ºtermo de uma PG(A¹,A²,A³...)
A) A4=375 e Q=5



B) A4=128 e Q=4


C) A5=10³ e Q=10

Answer 1

$a)a_n=a_1.q^{(n-1)}\\\\a_4=a_1.q^{(4-1)}\\\\a_4=a_1.q^3\\\\375=a_1.5^3\\\\375=a_1.125\\\\a_1= \frac{375}{125}\\\\a_1=3\\\\\\b)a_4=a_1.q^3\\\\128=a_1.4^3\\\\128=a_1.64\\\\a_1= \frac{128}{64}\\\\a_1=2\\\\\\c)a_5=a_1.q^4\\\\10^3=a_1.10^4\\\\a_1= \frac{10^3}{10^4}\\\\a_1= \frac{1}{10}\\\\a_1=0,1\\\\\\\\Renato.$