问题
解答题
已知a是方程2x2+3x-1=0的一个根，求代数式
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答案
∵a是方程2x2+3x-1=0的一个根
∴2a2+3a-1=0即2a2+3a=1
原式=
| 2a5+3a4+3a3+9a2-5a+1 |
| 3a-1 |
=
| a3(2a2+3a)+3a3+9a2-5a+1 |
| 3a-1 |
=
| 4a3+9a2-5a+1 |
| 3a-1 |
=
| 2a(2a2+3a)+3a2-5a+1 |
| 3a-1 |
=
| 3a2-3a+1 |
| 3a-1 |
=
| ||||
| 3a-1 |
=
| ||||
| 3a-1 |
=
| ||||
| 3a-1 |
=-
| 5 |
| 2 |