问题标题：
【arectangulargameboardiscomposedofidenticalsquaresarrangedinarectangulararrayofrrowsa:r^2-rb:r^2-1c:r^2d：r^2+1e:r^2+rarectangulargameboardiscomposedofidenticalsquaresarrangedinarectangulararrayofrrowsandr+1columns.t】
问题描述：
arectangulargameboardiscomposedofidenticalsquaresarrangedinarectangulararrayofrrows
a:r^2-r
b:r^2-1
c:r^2
d：r^2+1
e:r^2+r
arectangulargameboardiscomposedofidenticalsquaresarrangedinarectangulararrayofrrowsandr+1columns.therrowsarenumberedfrom1throughr,andther+1columnsarenumberedfromrthroughr+1，if人》10，whichofthefollowingrepresentsthenumberofsquaresontheboardthatareneitherinthe4thrownorinthe7thcolumn
卜旭辉回答：
本题选a!
就是r*(r+1)格中去掉第4行第7列的格子后还有几格,
所以
共有:r*(r+1)-(r+r+1)+1
=r^2+r-2r-1+1=r^2-r.
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