是1/a 再减2还是1/（a-2）?如果是前面这种的话,答案就为-3
2a^4+6a^3-5a+1/a -2
=2a^2(a^2+3a)-5a+1/a -2
=-2a^2-5a+1/a -2
=-2(a^2+3a)+a+1/a -2
=2+a+1/a -2
=a+ 1/a
=(a^2+1)/a
=-3a/a
=-3