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等差数列an求法分步解析3类典型例题带你掌握核心方法:从公式拆解到高考实战全攻略

投稿2025-05-28 09:39:11

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涓€銆佸熀纭€鍏紡娉曪細鏁板鑰佸笀鐨勪紶瀹跺疂 馃攽

鈥?strong>鈥嬫牳蹇冨彛璇€鈥?/strong>鈥嬶細鈥?strong>鈥嬮椤?锛坣-1锛変箻鍏樊鈥?/strong>鈥?br/> 杩欎釜鍏紡灏卞儚鍋氳彍鏃剁殑鐩愶紝鐪嬬潃绠€鍗曚絾绂讳簡瀹冪粷瀵逛笉琛岋紒涓句釜鏍楀瓙锛氬凡鐭鈧?8锛宎鈧?20锛屾眰閫氶」鍏紡銆?br/> 鈥?strong>鈥嬭В棰樹笁姝ヨ蛋鈥?/strong>鈥嬶細

  1. 鍒楁柟绋嬬粍锛?br/> a鈧?2d=8
    a鈧?6d=20
  2. 娑堝厓瑙f柟绋嬶細
    涓ゅ紡鐩稿噺寰?d=12 鈫?鈥?strong>鈥媎=3鈥?/strong>鈥?br/> 甯﹀洖寰椻€?strong>鈥媋鈧?2鈥?/strong>鈥?/li>
  3. 濂楀叕寮忥細
    鈥?strong>鈥媋n=2+3(n-1)=3n-1鈥?/strong>鈥?/li>

鈿狅笍 鈥?strong>鈥嬮伩鍧戞寚鍗椻€?/strong>鈥嬶細

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  • 閬囧埌鏂囧瓧搴旂敤棰橈紙姣斿缃戦〉6鎻愬埌鐨勫缓绛戝伐绋嬭绠楋級锛屽厛鐢诲浘鏍囨敞宸茬煡閲忓啀鍔ㄦ墜

浜屻€侀€掓帹鍏紡杞寲锛氭暟瀛︾晫鐨勫彉褰㈤噾鍒?馃殫

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杩欑棰樼湅鐫€鍚撲汉锛屽叾瀹炲氨鏄€?strong>鈥嬬焊鑰佽檸鈥?/strong>鈥嬶紒
鈥?strong>鈥嬭В棰樼绫嶁€?/strong>鈥嬶細

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  2. 鐩存帴濂楀熀纭€鍏紡锛?br/> 鈥?strong>鈥媋n=2+5(n-1)=5n-3鈥?/strong>鈥?/li>

浣嗛亣鍒拌繘闃剁増鍛紵姣斿缃戦〉5鐨勪緥棰橈細a鈧欌倞鈧?3a鈧?2
杩欐椂鍊欏氨瑕佺敤鈥?strong>鈥嬫瀯閫犳硶鈥?/strong>鈥嬶細

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鈥?strong>鈥嬪疄鎴樻紨缁冣€?/strong>鈥嬶細宸茬煡Sn=2n虏+3n

  1. 璁$畻a鈧?S鈧?5
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  3. 楠岃瘉a鈧佹槸鍚︾鍚堬細褰搉=1鏃?脳1+1=5 鉁旓笍

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涓夌被棰樺瀷瀵规瘮瀹濆吀 馃摎

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涓汉琛€娉粡楠?馃挃

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