Question

Dacă b3=2si b5=4 sunt 2 termeni ai unei progresii geometrice, determinați b7

Answer 1

b3=b1*q^2.
b5=b1*q^4.
q^2=2/b1
4=b1*4/b1^2
4b1=4
b1=1
2=b1*q^2
q=$\sqrt{2}$
b7=b1*q^6
b7=$\sqrt{2}$^6
b7=8

Answer 2

[tex]\it b_5 = b_3\cdot q^2 \Longrightarrow q^2 = \dfrac{b_5}{b_2} = \dfrac{4}{2} = 2 \\\;\\ \\\;\\ b_7 = b_5\cdot q^2 = 4\cdot 2 = 8[/tex]