Why did they do that with the answer? (Geometric sequence and index notation)

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jojo55
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Howdy .

I don't get why part (ii) changes the first line of the answer. They start using index laws.

Is this necessary for the A-level exam as I don't understand why they are doing that in the first place .

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DFranklin
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They've done it to reduce it to a "simpler" form. Note that what's simple is somewhat a matter of taste: I would consider -80 \times \left(-\frac{1}{2}\right)^n the simplest form for the answer myself.
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