Geometric sequence 3

In geometric sequence is a4 = 40; a9= 1280; sn=2555. Calculate the first item a1, quotient q, and n - number of members by their sum s_n.

Final Answer:

a1 =  5
q =  2
n =  9

Step-by-step explanation:

a4=a1q3=40 a9=a1q8=1280  128040=q8q3  0.03125=q5 0.031250.2=q q=2  a4=a1q3=a123=40 a1=2340=5
 sn=2555=a1q1qn1=212n1 511=2n1 512=2n ln512=nln2  n=ln2ln512 n=9



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