中考真题的分数化简与评价
= 2(1-9a^4)/[2b？(3a？-1)]
=[(1-3a？)(1+3a？)]/[b？(3a？-1)]
= -(1+3a？)/b？
将a = 3，b=2 b = 2代入上述简化公式，我们得到:
=-(1+3*3?)/2?
=-28/4
=-7
=[(1-3a？)(1+3a？)]/[b？(3a？-1)]
= -(1+3a？)/b？
将a = 3，b=2 b = 2代入上述简化公式，我们得到:
=-(1+3*3?)/2?
=-28/4
=-7