Asked by ernesto

if the 3rd,5th and 11th terms are distinct and form a geometric sequence, what is the 2020th term if then 4th term is 5?
Answered by ernesto
please show how to solve the problem...
Answered by Annora Beatrice Monrrow
Um... i'm sorry as soon as I say this I was completely lost- sorry!!!!!!
Answered by R_scott
a + 3d = 5 ... a = 5 - 3d

(a + 4d) / (a + 2d) = (a + 10d) / (a + 4d) ... "cross" multiply

a^2 + 8ad + 16d^2 = a^2 + 12ad + 20d^2 ... subtract a^2

8ad + 16d^2 = 12ad + 20d^2 ... divide by 2d

4a + 8d = 6a + 10d ... substituting ... 20 - 12d + 8d = 30 - 18d + 10d

solve for d , then substitute back to find a
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