Find the missing term of each geometric sequence. It could be the geometric mean or it’s opposite.

Question

1.) 4, ?, 16

2.) 9, ?, 16

Answer 1

Well suppose the common ratio is r, and the missing term is x

Then

4r = x

rx = 16

So dividing

4/x = x/16

so cross multiplying

x² = 4 x 16 = 64, so x = 8

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Try (2) yourself using the same idea