1/2x,-2/3x^2,3/4x^3,-4/5x^4,5/6x^5……写出第10个?第n个?

单项式2x,-4x^3,8x^5,-16x^7,32x^9,写出第N个单项式 1/x,-2/x^2,4/x^3,-8/x^5,16/x^5,第n个分式是? 有一串单项式:-X,2X^2,-3X^3,4X^4,...,-19X^19,20X^20,...请写出第N个,第（N+1 x,-2x^2,3x^3,-4x^4,5x^5,-6x^6……第n个式子是多少 观察下列一组单项式：-x^2,2x^4,-3x^6,4x^8……请你写出第n个单项式,然后回答第n x,-2x^2,3x^3,-4x^4.-100x^100写出第n个单项式 找规律,-x,2x^2,-3x^3,4x^4…,-19x^19,20x^20…请根据规律写出第n个单项式 下列单项式-x,2x二次方,-3x三次方,4x四次方,……,-19x十九次方 写出第n个,第n+1个单项式 观察下列单项式-x^2,3x^4 ,-5x^6 ,7x^8 ,-9x^10 ,根据你发现的规律,写出第2009个单项式是 x^2/3,-x^3/15,x^4/35,-x^5/63,x^6/99,照此规律,第十个式子是( ),第n个识式子是( 观察：-x,3x^2,-5x^3,7x^4,...,-37x^19,39x^20,第n个式子是? x,-2x的二次方,3x的三次方,4x的四次方,.,-10x的十次方,请你写出第N个单项式