判别下列级数是否收敛 若收敛是绝对收敛还是条件收敛?

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判别下列级数是否收敛,若收敛是绝对收敛还是条件收敛?

热搜:幂级数收敛域的求解方法有几种

答案解析

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  • 利用比较审敛法的极限形式,因为
       latex.action?latex=XGxpbSBfe25cdG8gXGluZnR5IH1cZnJhY3t8YV9ufH17XGZyYWN7MX17bn19PVxsaW0gX3tuXHRv%0D%0AIFxpbmZ0eSB9XGZyYWN7ZV57XGZyYWN7MX17bn19LTF9e1xmcmFjezF9e259fQ%3D%3D
       latex.action?latex=PVxsaW0gX3tuXHRvIFxpbmZ0eSB9XGZyYWN7KGVee1xmcmFjezF9e259fS0xKSd9e1xsZWZ0KCBc%0D%0AZnJhY3sxfXtufSBccmlnaHQpJ309Me%2B8njA%3D
       所以级数latex.action?latex=XHN1bSBfe249MX1ee1xpbmZ0eSB9fGFfbnw%3D发散.
       又由莱布尼兹审敛法,因为
       latex.action?latex=dV9uPWVee1xmcmFjezF9e259fS0x77yeZV57XGZyYWN7MX17bisxfX0tMT11X3tuKzF9,latex.action?latex=XGxpbSBfe25cdG8gXGluZnR5IH0oZV57XGZyYWN7MX17bn19LTEpPTA%3D
       故所给级数条件收敛。$因为latex.action?latex=XHN1bSBfe249MX1ee1xpbmZ0eSB9fHVfbnw%3D为p-级数latex.action?latex=XHN1bSBfe249MX1ee1xpbmZ0eSB9XGZyYWN7MX17bl5wfQ%3D%3D,由其收敛性可知
       当p>1时,原级数绝对收敛;
       当0<p≤1时,latex.action?latex=XHN1bSBfe249MX1ee1xpbmZ0eSB9XGZyYWN7MX17bl5wfQ%3D%3D发散.又latex.action?latex=fHVfbnw9XGZyYWN7MX17bl5wfe%2B8nlxmcmFjezF9eyhuKzEpXnB9PXx1X3tuKzF9fA%3D%3D,latex.action?latex=XGxpbSBfe25cdG8gXGluZnR5IH1cZnJhY3sxfXtuXnB9PTA%3D,于是原级数条件收敛;
       当p≤0时,latex.action?latex=XGxpbSBfe25cdG8gXGluZnR5IH1cZnJhY3sxfXtuXnB9XG5lcSAw,由级数收敛的必要条件可知原级数是发散的.
       综上所述:级数latex.action?latex=XHN1bSBfe249MX1ee1xpbmZ0eSB9KC0xKV57bi0xfVxmcmFjezF9e25ecH1cbGVmdFx7XGJlZ2lu%0D%0Ae2FycmF5fXtjY33nu53lr7nmlLbmlZvvvIwgJuW9k3DvvJ4x5pe2IFxc5p2h5Lu25pS25pWb77yM%0D%0AICblvZMw77yccFxsZXEgMeaXtiBcXOWPkeaVo%2B%2B8jCAm5b2TcFxsZXEgMOaXtlxlbmR7YXJyYXl9%0D%0A