1.-x+2y=6
所以x-2y=-6
3(x-2y)²-5(x-2y)+6
=3×(-6)²-5×(-6)+6
=108+30+6
=144
选C
2.x=-1
ax³+bx+1=-a-b+1=6
a+b=-5
x=1时
ax³+bx+1=a+b+1=1-5=-4
选C
3.
第十个代数式是__-99x的十次方___.
4.a-b-1=0
a-b=1
2007-2008a+2008b
=2007-2008(a-b)
=2007-2008
=-1
5.[（x+y）（－）(x-y)]（－）3x
=[3(x+y)+2(x-y)]（－）3x
=(5x+y)（－）3x
=3(5x+y)+2×3x
=15x+3y+6x
=21x+3y
不知道x和y,所以无法计算
5.化简求值
-2x²-1/2[3y²-2（x²-y²）+6]
=-2x²-3/2y²+x²-y²-3
=-x²-5/2y²-3
=-4-5/8-3
=-61/8