1x2/1+2x3/1+3x4/1+.+2009x2010/1=? 2x4/1+4x6/1+6x8/1+.+2010x2012/1=?很急!1!

切点(a,a³+2)
y'=3x²
斜率k=3a²
所以切线是y-(a³+2)=3a²(x-a)
y=kx过原点
-a³-2=-3a²
a³-3a²+2=0
(a-1)(a²-2a-2)=0
a=1,a=1±√2
k=3a²
k=3
k=9-6√2
k=9+6√2

1x2/1+2x3/1+3x4/1+.+2009x2010/1
=1-2/1+2/1-3/1+3/1-4/1+……+2009/0-2010/1
=1-2010/1
=2010/2009
2x4/1+4x6/1+6x8/1+.+2010x2012/1
=2/1x(2/1-4/1+4/1-5/1+5/1-8/1+……+2010/1-2012/1)
=2/1x(2/1-2012/1)
=4024/1005