Odpowiedzi

2009-04-17T16:35:47+02:00
A2=4 i a5=0,5

a₁ * q = 4
a₁ * q⁴ = 0.5 dzielimy stronami

q/ q⁴ = 8
q⁻³=8
q=0.5

a₁ * 0.5= 4
a₁=8
an=8 * (0.5) do potegi (n-1)

S₆=a₁ (1-q⁶/1-q)
S₆=8 * (1- 1/64) / 1/2
S₆ =16 * 63/64 = 1008/64 = 15.75
2009-04-17T16:36:49+02:00
Dane:a2=4 i a5=0,5

z def c. geom--->
a2=a1q
a5=a1q₄ dziele stronami
q³=a5/a2=1/2:4=1/(2³)
q=1/2
a1=a2/q=8
wzor na an=a1*q^(n-1)=8*(1/2)^(n-1)

S6=a1*(1-q^n)/(1-q)
s6=8*(1-1/2⁶)/(1/2)
S₆=8 * (1- 1/64) / 1/2
S₆ =16 * 63/64 = 1008/64 = 15.75