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7．已知P=(1+1/(1+2)+1(1+2+3)+ 1/(1+2+3+4)+…+1/(1+2+3+…2007)×2008/(2007~2×2)．求P~(-1)的值．8．已知x=2007时,代数式ax~7+bx~5+ cx~3+dx-1的值是2007．求当x=-2007时,代数式ax~7+bx~5+cx~3+dx+1的值．9．计算1/2+(1/3+2/3)+(1/4+2/4+3/4)+
7. It is known that P=(1+1/(1+2)+1(1+2+3)+ 1/(1+2+3+4)+...+1/(1+2+3+...2007) ×2008/(2007~2×2). Find the value of P~(-1). 8. When x=2007 is known, the value of algebraic expression ax~7+bx~5+cx~3+dx-1 is 2007. When seeking x=-2007, the value of algebraic expression ax~7+bx~5+cx~3+dx+1.9. Calculate 1/2+(1/3+2/3)+(1/4+ 2/4+3/4)+