求下列函数的单调区间:(1)y=-x³-2x²-4x+5(2)y=(x+1)(x²-1)(3)y=4x²+1/x(4)y=xlnx
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![求下列函数的单调区间:(1)y=-x³-2x²-4x+5(2)y=(x+1)(x²-1)(3)y=4x²+1/x(4)y=xlnx](/uploads/image/z/11547228-12-8.jpg?t=%E6%B1%82%E4%B8%8B%E5%88%97%E5%87%BD%E6%95%B0%E7%9A%84%E5%8D%95%E8%B0%83%E5%8C%BA%E9%97%B4%EF%BC%9A%EF%BC%881%EF%BC%89y%3D-x%26%23179%3B-2x%26%23178%3B-4x%2B5%EF%BC%882%EF%BC%89y%3D%EF%BC%88x%2B1%EF%BC%89%EF%BC%88x%26%23178%3B-1%EF%BC%89%EF%BC%883%EF%BC%89y%3D4x%26%23178%3B%2B1%2Fx%EF%BC%884%29y%3Dxlnx)
求下列函数的单调区间:(1)y=-x³-2x²-4x+5(2)y=(x+1)(x²-1)(3)y=4x²+1/x(4)y=xlnx
求下列函数的单调区间:
(1)y=-x³-2x²-4x+5(2)y=(x+1)(x²-1)(3)y=4x²+1/x(4)y=xlnx
求下列函数的单调区间:(1)y=-x³-2x²-4x+5(2)y=(x+1)(x²-1)(3)y=4x²+1/x(4)y=xlnx
(1)y=-x³-2x²-4x+5
y'=-3x^2-4x-4=0
3x^2+4x+4=0
△=4^2-4*4*30 单调增
当-10 单调增
(3)y=4x²+1/x
y'=8x-1/x^2
y'=0
(2x)^3-1=0
2x-1=0
x=1/2
当 x0,单调增
(4)y=xlnx
y'=lnx+x*1/x
=lnx+1
y'=0
lnx=-1
x=1/e
当00 单调增