1條dse數學問題

Question

Lily is building towers of playing cards with more and more storeys. 
http://upload.lsforum.net/users/public/h23905card1i192.gif

Find the difference between the number of cards in the n-storey card tower and the (n-1)-storey card tower.

Ans.:
http://upload.lsforum.net/users/public/t4643card2n192.gif

我唔明點解係5+3(n-2)而不是5+3(n-1)...
希望大家能幫忙解釋一下,thz!

mLee · Accepted Answer

T(1) = 2
T(2) = 2+5 = 7
T(3) = 2+5+8 = 15
T(2) - T(1) = 5 ... d(1) = 5
T(3) - T(2) = 8 ... d(2) = 5+3(1)
T(4) - T(3) = 11 . d(3) = 5+3(2)
...
T(n) - T(n-1) = d(n-1) = 5+3(n-1-1) = 5+3(n-2)

If you don't understand, pm me la

1條dse數學問題

1 個解答