Question

sa se determine primii doi termeni ai progresiei geometrice (bn) daca b8 este 256 si q este 4

Answer 1

b₈=256,   q=4
b₈=256=>b₁x4⁸⁻¹=256=>b₁x4⁷=256=>b₁x4⁷=4⁴=>b₁=4⁴:4⁷=>

=>b₁=4⁴⁻⁷=4⁷⁻³=>b₁=1supra 4³=>b₁=1 supra 64.

b₂=b₁x4²⁻¹=>b₂=b₁x4¹=>b₂=1 supra 64x 4=> b₂=4supra 64=>
=>b₂=1 supra 16

Answer 2

$b_1=\dfrac{b_8}{q^7}=\dfrac{256}{4^7}=\dfrac{4^4}{4^7}=\dfrac{1}{4^3}=\dfrac{1}{64}$

$b_2=b_1\cdot q=\dfrac{1}{64}\cdot4 = \dfrac{1}{16}$