Geometric sequence

In the geometric sequence, is a4 = 20 a9 = -160. Calculate the first member a1 and quotient q.

Final Answer:

q =  -1.5157
a1 =  -5.7435

Step-by-step explanation:

a4=20 a9=160  a9 = q5 a4  q = 5a9/a4 q<0 +++ q=5160/20=1.5157
a4=q3 a1  a1=a4/q3=20/(1.5157)35.7435   Verifying Solution:   A4=a1 q3=(5.7435) (1.5157)3=20 A9=a1 q8=(5.7435) (1.5157)8=160



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