求这三道题的过程,急!!
2个回答
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(1)
lim(x->2) (x^2-3x+2)/(x^2-x-2)
=lim(x->2) (x-2)(x-1)/[(x-2)(x+1)]
=lim(x->2) (x-1)/(x+1)
=1/3
(2)
lim(x->+∞) (3x^2+4x-5)/(7x^2+2x-3)
=lim(x->+∞) (3+4/x-5/x^2)/(7+2/x-3/x^2)
=3/7
(3)
y=2x^2+lnx
y'=4x + 1/x
y'' =4 - 1/x^2
lim(x->2) (x^2-3x+2)/(x^2-x-2)
=lim(x->2) (x-2)(x-1)/[(x-2)(x+1)]
=lim(x->2) (x-1)/(x+1)
=1/3
(2)
lim(x->+∞) (3x^2+4x-5)/(7x^2+2x-3)
=lim(x->+∞) (3+4/x-5/x^2)/(7+2/x-3/x^2)
=3/7
(3)
y=2x^2+lnx
y'=4x + 1/x
y'' =4 - 1/x^2
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