prove by mi that:
1+2+3+...+n=1/2n(n+1)
..............(之前有好多step,不過唔重要,我主要既問題係下面)
for any positive integerk,assume thatp(k) is true.ie> 1+2+3+...+k=1/2k(k+1)
then1+2+3+...+k+(k+1)=1/2k(k+1)+(k+1)
=1/2(k+1)(k+2) ←←←←
︰
︰
我就係唔明←←←←個度係點樣變出黎既.希望解答
同埋我都想問,1+2+3個d野係咪計數個時唔洗理佢?