Question

有一个长方形,长是六个格子宽是四个格子,一共有多少个长方形?

Answer 1

1 1 1 1 1 1

1 1 1 1 1 1

1 1 1 1 1 1

1 1 1 1 1 1

c1,6*c2,4+c1,6*c3,4+c1,6*c4,4=(c1,6)*(2^4-c1,4)

c1,6*c1,4+c1,6*c3,4+c1,6*c4,4=(c2,6)*(2^4-c2,4)

(c3,6)*(2^4-c3,4)=

(c4,6)*(2^4-c4,4)

(c5,6)*2^4

全部相加等于(2^6-2)*2^4-24-90-120-15