Geometric sequence 3

In geometric sequence is a8 = 312500; a11= 39062500; sn=1953124. Calculate the first item a1, quotient q, and n - number of members by their sum s_n.

Correct answer:

a1 =  4
q =  5
n =  9

Step-by-step explanation:

a8=a1q7=312500 a11=a1q10=39062500  39062500312500=q10q7  0.008=q3 0.0080.33333333333333=q q=5  a8=a1q7=a157=312500 a1=57312500=4
 sn=1953124=a1q1qn1=515n1 1953124=5n1 1953125=5n ln1953125=nln5  n=ln5ln1953125 n=9

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