8;4 S5-? 1,5;3 S5-? В4=1\16 В5=1\64 S5-? q=-2/3 S4=65 B1=?

Question

8;4

S5-?

1,5;3

S5-?

В4=1\16

В5=1\64

S5-?

q=-2/3

S4=65

B1=?

Answer 1

1)

b1=8,b2=4

q=4/8=0,5

S5=a1*(q^n-1)*5/q-1=8*(0,5^5-1)*5/0,5-1=77,5

2)

b1=1,5.b2=3

q=3/1.5=2

S5=a1*(q^n-1)*5/q-1=1.5*(2^5-1)*5/2-1=232,5

 

В4=1\16

В5=1\64

q=1/64:1/16=1/4

a1=a4/q^3=4

S5=a1*(q^n-1)*5/q-1=4*(1/4^5-1)*5/1/4-1= -6