請問我可以寫成--當n=k+1時,左式 : 1*2+2*3+.....+k(k+1)+(k+1)(k+2)=1/3k(k+1)(k+2)+(k+1)(k+2)=(k+1)(k+2)(1/3k+1) 右式 : 1/3(k+1)(k+2)(k+3)=(k+1)(k+2)(1/3k+1)嗎?