请教一个数学题

hot_1214UID: 3221942

A rectangular game board is composed of identical squares arranged

in a rectangular array of r rows and r+1 columns. The r rows are numbered

from 1 through r, and the r+1 columns are numbered from 1 through r+1.

If r>10, which of the following represents the number of squares on the boars

that are neither in the 4th row nor in the 7th column?

A  r2-r

B  r2-1

C  r2

D r2+1

E  r2+r

r2就是r的平方，这里木有显示出来。。。

木有搞懂呀。。。。。。答案是A

mlq90103UID: 3253083

我理解的
去掉一行一列不就是

((r+1)-1)*((r)-1)=r(r-1)=r2-r,答案A

hua11UID: 3027785

同意楼上的，哈哈

hot_1214UID: 3221942

2# mlq90103
原来如此。谢之！！

诡异的小sunUID: 3278905

吐个槽...
还可以直接算:R2-R-(R+1)+1=R2-R

polymeraseUID: 3142603

5L算差了吧…总格数是R×(R+1)