更新时间2020-10-28 12:00:06
y' = (1/4)[ 2( x - 3 )( x - 1 ) - ( x - 3 )^2 ]/( x - 1 )^2
= (1/4)[ x^2 - 2x - 3 ]/( x - 1 )^2
= (1/4)( x - 3 )( x + 1 )/( x - 1 )^2 = 0
驻点 x1 = 3,x2 = -1;
x = 1 是第二类间断点;
y'' = (1/4)[ ( 2x - 2 )( x - 1 )^2 - 2( x - 1 )( x - 3 )( x + 1 ) ]/( x - 1 )^4
y''(-1) = (1/4)[ -16 - 0 ]/(-2)^4 < 0,驻点 x = -1 是极大点;
y''(3) = (1/4)[ 16 - 0 ]/(2)^4 > 0,驻点 x = 3 是极小点;
故函数没有拐点,极大点左右是凸区间,极小点左右是凸区间;
单调增区间是 ( -∞,-1 )∪( 3,∞ );单调减区间是 ( -1,1 )∪( 1,3 );
y(-1) = [ ( -1 - 3 )^2 ]/[ 4( -1 - 1 ) ] = -2,极大值是 -2;
y(3) = [ ( 3 - 3 )^2 ]/[ 4( 3 - 1 ) ] = 0,极小值是 0;
凹区间是 ( 1,∞ ),凸区间是 ( -∞,1 ) 。
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