研究所、轉學考(插大)-微積分題庫

2. The price-earnings ratio (PE ratio) of a stock is given by

R(x, y) =
where x denotes the price per share of the stock and y denotes the earnings
per share. Estimate the change in the PE ratio of a stock if its price
increases from $60/share to $62/share while its earnings decrease from
$4/share to $3.80/share. (15%)