1+2+3+4+5+6一直加到n ，再+2为什么等于2的n次方
\uff081\uff09 2\u7684100\u6b21\u65b9\u52a0\u4e0a\u8d1f2\u7684101\u6b21\u65b9 \u7b49\u4e8e\u591a\u5c11 \u8c22\u8c22 \uff082\uff09 2\u7684n\u6b21\u65b9\u7b49\u4e8ea\uff0c3\u7684n\u6b21\u65b9\u7b49\u4e8eb\uff0c\u6c426\u7684n\u6b21\u65b9 \u8c22\u8c22\u89e3\uff1a\uff081\uff092^100+(-2)^101=2^100-2*2^100=-2^100
\uff082\uff092^n*3^n=6^n=ab
2^n+2^n-3\u00d72^(n+1)
=2\u00d72^n-3\u00d72^(n+1)
=2^n-3\u00d72^(n+1)
=-2\u00d72^(n+1)
=-2^(n+2)
=(n²+n+4)/2
当n=4,
1+2+3+4+2=12
2^4=16
哈哈，不对了吧
1+2+3+4+5+6一直加到n = （n+1）n /2
在+2 = （n+1）n /2 +2 =( N^2+N +4 ) /2
1+2+3+……+n+2=(1+n)*n/2+2
绛旓細1+2+3+4+5+6+鈥+n =(1+n)脳n梅2 =n(n+1)/2 绫讳技浜庢褰㈢殑闈㈢Н鍏紡锛岃繖鏍风殑寮忓瓙缁撴灉=(绗1涓暟+鏈鍚1涓暟)脳涓暟(澶氬皯涓暟)梅2
绛旓細1+2+3+4+5+6涓鐩村姞鍒50绛変簬1275銆傝绠楁柟娉曞涓嬶細S50=锛坅1+a50锛壝梟梅2 =锛1+50锛壝50梅2 =1275 杩欎釜鏄瓑宸暟鍒楁眰鍜岀殑闂锛宎1=1锛宯=50锛宎50=50锛宒=1锛屾眰S50銆
绛旓細鎵浠ユ渶缁堢瓟妗堝氨鏄100脳49+50+100=100脳50+50=5050
绛旓細娉1锛1+2+3+4+5+鈥︹+100 =100脳(1+100)梅2 =5050 娉2锛1+2+3+4+5+鈥︹+99+100 =(1+100)+(2+99)+(3+98)+鈥︹+(50+51)=101脳50 =5050 鍙傝冭祫鏂欙細浠呬緵鍙傝冿紝绁濇偍瀛︿範杩涙锛
绛旓細1+2+3+...+365=66795 瑙傚療寮忓瓙鍙互鐪嬪嚭鍚庝竴涓暟姣斿墠涓涓暟澶1锛屽埄鐢ㄧ瓑宸眰鍜屽叕寮忥細Sn=n(a1+an)/2锛岄椤逛负1锛屾湯椤逛负365銆=锛1+365锛/2脳365 =366/2脳365 =183脳365 =66795
绛旓細绛旀鏄325銆備娇鐢ㄧ瓑宸暟鍒楁眰鍜岀殑鏂规硶锛氶氶」鍏紡 an=a1+(n-1)d 锛屾敞鎰忥細绛夊樊鏁板垪姹傚拰鍏紡 鍗 绗琻椤=棣栭」+(n-1)脳鍏樊锛坣鏄」鏁帮級鍓峮椤瑰拰鍏紡 1+2+3+4+5+6渚濇鍔犲埌25 =锛1+25锛墄25梅2 =26x25梅2 =325
绛旓細1+2+3+4+5+6+...+356=63546 瑙ｏ細鏍规嵁绛夊樊鏁板垪姹傚拰鍏紡锛屽緱 1+2+3+4+5+6+...+356 =356*1+356*锛356-1锛*1/2 =356+356*355/2 =356+63190 =63546
绛旓細1+2+3+...+365 =锛1+365锛/2脳365 =366/2脳365 =183脳365 =66795 鍒╃敤绛夊樊鏁板垪姹傚拰鍏紡绠鍗曟眰瑙ｏ紝棣栭」涓庡熬椤瑰拰鐨勪竴鍗婁箻浠ユ婚」銆
绛旓細1+2+3+4+...+97+98+99+100锛濓紙1+100锛+锛2+99锛+锛3+98锛+...+锛50+51锛夛紳锛1+100锛*50锛101*50锛5050绛旓細1鍗2鍗3鍗4鍗5鍗6涓鐩村姞鍒100绛変簬5050銆
绛旓細绛旀锛11325銆傝繖鏄竴閬撶瓑宸暟鍒楁眰鍜岄棶棰橈紝鍙互鐢ㄧ瓑宸暟鍒楁眰鍜屽叕寮忚绠椼傞椤规槸1銆佹渶鍚庝竴椤规槸150锛屼袱椤圭浉鍔狅紝鍜屼负150+1=151銆備竴鍏辨湁150梅2=75缁勶紝151脳75=11325銆
