1十3十5十7十······十99(递等式) 1十3十5十7十9十···十99等于多少
\u8ba1\u7b97(1\u53413\u53415\u53417\u5341\u00b7\u00b7\u00b7\u00b7\u00b7\u534199)\u4e00(2\u53414\u53416\u53418\u5341\u00b7\u00b7\u00b7\u00b7\u00b7\u534198)\u7684\u503c\u89e3\uff1a\u539f\u5f0f=(1-2)+(3-4)+\u2026\u2026+\uff0897-98\uff09+99
=-1-1-1-\u2026\u2026-1+99
=\uff08-1\uff09\u00d749+99
=-49+99
=50
1\u53413\u53415\u53417\u53419\u5341\u00b7\u00b7\u00b7\u534199
=\uff081+99\uff09x50\u00f72
=100x25
=2500
(1+99)×99÷2
1+3+5+7+……+99
=(1+99)×[(99-1)÷2+1]÷2
=100×50÷2
=2500
绛旓細1+3+5+7+鈥︹+85+87+89 =锛1+89锛*45/2=45^2=2025 2025-25=2000锛1+3+5+7+...杩欎釜绠楁槸涓鐩村姞鍒89锛屽啀鍑忓幓25寰楀埌鐨勫拰鏄2000銆
绛旓細1+3鍗5鍗7鍗...鍗(2n-1)=(1+2n-1)*n/2 = n^2 锛坣鐨勫钩鏂癸級浠e叆绗竴棰,n=17,2n-1=2*17-1=33 鎵浠ョ涓棰橈細1鍗3鍗5鍗7鍗伮仿仿峰崄(33)=17x17
绛旓細=250000 鎴 1鍗3鍗5鍗7鍗鈥︹﹀崄997+999 =500²=250000
绛旓細1鍗3鍗5鍗7鍗...37鍗39=400.鐢ㄧ畝渚挎柟娉曡绠 1+39=40,3+37=40,5+35=40,7+33=40,9+31=40,11+29=40,13+27=40,15+25=40,17+23=40,19+21=40,40*10=400.
绛旓細鏂规硶涓锛1+3+5+7+9+11+13+15+17+19鐨勭畝渚胯繍绠 =锛1+19锛壝5 =20脳5 =100 鏂规硶浜岋細1+3+5+7+9+11+13+15+17+19 =锛1+19锛壝10梅2 =20脳10梅2 =200梅2 =100
绛旓細1鍗3鍗5鍗7鍗锛庯紟锛庡崄17鍗19 =锛1+19锛墄10梅2 =20x5 =100
绛旓細杩欐槸绛夊樊鏁板垪锛屽叕宸=2锛岄」鏁=(6n+1-1)梅2+1=3n+1锛屽拰=锛1+6n+1锛壝楋紙3n+1锛壝2=锛3n+1锛²
绛旓細杩欓亾棰樼殑棣栧熬鐩稿姞閮芥槸20锛屾瘮濡1+19銆3+17銆5+15绛夌瓑锛屾诲叡鏄5瀵癸紝鍥犳 =(1+19)脳5 =20脳5 =100
绛旓細1+3+5+7...+95+97+99璁$畻鏂规硶濡備笅锛1+3+5+7+路路路+95+97+99銆=锛1+99锛壝45梅2銆=100脳45梅2銆=50脳45銆=2250銆傜瓑宸暟鍒楀叕寮忥細绛夊樊鏁板垪鍏紡an=a1+(n-1)d銆傚墠n椤瑰拰鍏紡涓猴細Sn=na1+n(n-1)d/2銆傝嫢鍏樊d=1鏃讹細Sn=(a1+an)n/2銆傝嫢m+n=p+q鍒欙細瀛樺湪am+an=ap+aq銆傝嫢...
绛旓細棣栧熬涓や袱鐩稿姞锛岀瓟妗堟槸256