1﹚2>a>-1
ax+a+2>0,x=-2,a<2;x=1,a>-1.
2﹚2011
∵3x²-x=1,∴3x³-x²=x,6x³-2x²=2x.∵6x³+7x²-5x+2008=6x³-2x²+9x²-5x+2008,∴
6x³+7x²-5x+2008=2x+9x²-5x+2008=9x²-3x+2008=3﹙3x²-x﹚+2008=3+2008=2011.
3﹚4/3
A/﹙X-1)+B/(X+2)=A(X+2)/[﹙x-1﹚﹙x+2﹚]+B﹙X-1)/[﹙x-1﹚﹙x+2﹚]
=[A(X+2)+B﹙X-1)]/[﹙x-1﹚﹙x+2﹚],2x+3=A(X+2)+B﹙X-1)],A+B=2,2A-B=3,∴
A-B=4/3
4﹚1020
设:甲 乙 丙三种盆景分别为x,y,z盆,5x+10y+10z=2900,25x+20y+25z=3750,两式相减,得20x+10y+15z=850,两边乘1.2,得24x+12y+18z=1020.