观察下列运算并填空: 1×2×3×4+1=25=52; 2×3×4×5+1=121=112: 3×4×5×6+1=361=192;… 根据以上结果,猜想并研究:(n+1)(n+2)(n+3)(n+4)+1=_.
问题描述:
观察下列运算并填空:
1×2×3×4+1=25=52;
2×3×4×5+1=121=112:
3×4×5×6+1=361=192;…
根据以上结果,猜想并研究:(n+1)(n+2)(n+3)(n+4)+1=______.
答
由1×2×3×4+1=25=52=(02+5×0+5)2;
2×3×4×5+1=121=112=(12+5×1+5)2;
3×4×5×6+1=361=192=(22+5×2+5)2,…
观察发现:(n+1)(n+2)(n+3)(n+4)+1=(n2+5n+5)2.
证明:等式左边=(n+1)(n+2)(n+3)(n+4)+1
=(n2+3n+2)(n2+7n+12)+1
=n4+7n3+12n2+3n3+21n2+36n+2n2+14n+25
=n4+10n3+35n2+50n+25
=n4+2n2(5n+5)+(5n+5)2
=(n2+5n+5)2=等式右边.
故答案为:(n2+5n+5)2