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Calculate a7 for the geometric sequence with a1 = 4 and common ratio r=-2

Calculate a7 for the geometric sequence with a1 = 4 and common ratio r=-2-example-1

1 Answer

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The geometric sequence is given by the next formula:


a_n=a_1(r)^(n-1)

Where r represents the common ratio and n is the number for the sequence.

Now, we have the next given values:

r=-2

a1 =4

and we need to find a7, which means n=7.

Replacing on the geometric sequence formula:


a_7=-4(-2)^(7-1)
a_7=-4(-2)^6
a_7=-256

Then, the correct answer is option C.

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