Question

y/1*2+y/2*3+y/3*4+……+y/2008*2009=2008 求y,分有的是,

Answer 1

y/1*2+y/2*3+y/3*4+……+y/2008*2009=2008

y(1/1*2+1/2*3+.+1/2008*2009)=2008

y(1-1/2+1/2-1/3+1/3-1/4+.+1/2008-1/2009)=2008

y(1-1/2009)=2008

20086/2009=2008

y/2009=1

y=2009