(1)第4个算式为:4×6-52=24-25=-1;
(2)答案不唯一.如n(n+2)-(n+1)2=-1;
(3)一定成立.
理由:n(n+2)-(n+1)2=n2+2n-(n2+2n+1)
=n2+2n-n2-2n-1=-1.
故n(n+2)-(n+1)2=-1成立.
(1)第4个算式为:4×6-52=24-25=-1;
(2)答案不唯一.如n(n+2)-(n+1)2=-1;
(3)一定成立.
理由:n(n+2)-(n+1)2=n2+2n-(n2+2n+1)
=n2+2n-n2-2n-1=-1.
故n(n+2)-(n+1)2=-1成立.