well, you're asked to simply grab the second version of that amount, or balance, and provide a common factored version of it, is all
so [tex]\bf A_2=(P+Pr)+(P+Pr)r
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\textit{now, let's take common factor}
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A_2=\underline{(P+Pr)}+\underline{(P+Pr)} r\impliedby \textit{see the common factor?}
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A_2=\underline{(P+Pr)}(1+r)[/tex]
