Q. Find an explicit formula for the geometric sequence−25,−50,−100,−200,…. Note: the first term should be d(1).d(n)=
Identify Terms and Ratio: We need to identify the first term a1 and the common ratio r of the geometric sequence.The first term a1 is given as −25.To find the common ratio r, we divide the second term by the first term.r=(−50)/(−25)=2
Calculate Common Ratio: Now that we have the first term a1 and the common ratio r, we can write the explicit formula for the nth term of a geometric sequence, which is:d(n)=a1⋅r(n−1)Substitute a1=−25 and r=2 into the formula.d(n)=−25⋅2(n−1)
Write Explicit Formula: Let's perform a quick check to ensure that our formula is correct by plugging in n=1 to see if we get the first term of the sequence.d(1)=−25×2(1−1)=−25×20=−25×1=−25This matches the first term of the sequence, so our formula appears to be correct.
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