1的平方加2的平方加3的平方加---加到100的平方
一种方法(归纳猜想法):1、N=1时,1=1(1+1)(2×1+1)/6=1
2、N=2时,1+4=2(2+1)(2×2+1)/6=5
3、设N=x时,公式成立,即1+4+9+…+x2=x(x+1)(2x+1)/6
则当N=x+1时,
1+4+9+…+x2+(x+1)2=x(x+1)(2x+1)/6+(x+1)2
=(x+1)[2(x2)+x+6(x+1)]/6
=(x+1)[2(x2)+7x+6]/6
=(x+1)(2x+3)(x+2)/6
=(x+1)[(x+1)+1][2(x+1)+1]/6
综上所述,平方和公式1^2+2^2+3^2+…+n^2=n(n+1)(2n+1)/6成立,得证
n=100带进去。
绛旓細1脳1+2脳2+3脳3+4脳4+5脳5+6脳6+7脳7+8脳8+9脳9+10脳10 =1+4+9+16+25+36+49+64+81+100 =385 锛堟垜涓涓竴涓緵鑻︽墦瀛楀拰绠楃殑鍝!锛
绛旓細锛坣+1)^3-n^3=3n^2+3n+1 灏嗕笂寮忕疮鍔犺捣鏉ュ彲寰 锛坣+1)^3-1^3=3(1^2+2^2+3^2+...+n^2)+3(1+2+3+...+n)+n 鍙1^2+2^2+3^2+...+n^2=n(n+1)/2 鎵浠1鏂+2鏂+3鏂+鈥︹+n鏂=n(n+1)(2n+1锛/6
绛旓細鍥炵瓟锛1^2+2^2+3^2+...+n^2=n(n+1)(2n+1)/6
绛旓細=338350
绛旓細鎮ㄥソ锛佹湁涓涓叕寮=1鐨勫钩鏂瑰姞2鐨勫钩鏂瑰姞3鐨勫钩鏂瑰姞4鐨勫钩鏂瑰埌n鐨勫钩鏂=n涔樹互n+1涔樹互2n+1闄や互6 閭d箞 1鐨勫钩鏂瑰姞2鐨勫钩鏂瑰姞3鐨勫钩鏂瑰姞4鐨勫钩鏂瑰埌99鐨勫钩鏂 =99涔樹互99+1涔樹互2脳99+1闄や互6 =99涔樹互100涔樹互199闄や互6 =9900涔樹互199闄や互6 =1970100闄や互6 =328350 ...
绛旓細骞虫柟鍜屾眰鍜屽叕寮忥細1^2+2^2+鈥︹+n^2=n(n+1)(2n+1)/6 浠=2023锛屾鏃舵湁锛歯(n+1)(2n+1)/6=2023脳2024脳4047梅6=2761775324
绛旓細鏍规嵁鍏紡锛1^2+2^2+3^2+4^2+5^2+鈥+n^2=n(n+1)(2n+1)/6鎵浠 鍘熼=1^2+2^2+3^2+4^2+5^2+鈥+1000^2=1000脳1001脳2001/6=333833500绫讳技鐨勫叾瀹冭绠楀叕寮忚繕鏈夛細1+2+3+4+5+鈥+n=n(n+1)/2 1+3+5+7+9+11+13+15+鈥+(2n-1)=n^2 ...
绛旓細n^3-1=2*(1^2+2^2+3^2+...n^3-(n-1)^3=2*n^2+(n-1)^2-n 鍚勭瓑寮忓叏鐩稿姞 n^3-1^3=2*(2^2+3^2+.+n^2)=n^3+n^2+n(n+1)/鍒╃敤绔嬫柟宸叕寮 n^3-(n-1)^3=1*[n^2+(n-1)^2+n(n-1)]=n^2+(n-1)^2+n^2-n =2*n^2+(n-1)^2-n 2^3-1^3=...
绛旓細涓銆1骞虫柟+2骞虫柟+3骞虫柟+n骞虫柟鍏紡鏄細1²+2²+3²+...+n²=n(n+1)(2n+1)/6銆傚叿浣撴楠ゅ涓嬶細2³-1³=3脳1²+3脳1+13³-2³=3脳2²+3脳2+1...鎵浠ュ緱鍑猴細(n+1)³-n³=3n²+3n+1涓婇潰杩欎簺鐩稿姞寰楀埌锛...
绛旓細鍏紡锛1²+2²+3²+.+N²=n锛坣+1锛(2n+1)/6 1鐨勫钩鏂瑰姞鍒100鐨勫钩鏂 =100脳101脳201锛6=338350