# 问题内容:

In Mathematica, I can do expression replacement like x^2 -> x which changes power 2 of x into x. I wonder if there are any similar functionalities in sage?

```
R = PolynomialRing(ZZ, 2, "a")
a = R.gens()
(a[0] + a[1])^2
Out[173]:
a0^2 + 2*a0*a1 + a1^2
```

I would like to change all powers of a (> 1) into power 1. So replace a^k -> a for k >= 1.

So the desire output would be a0 + 2*a0*a1 + a1

## 原文地址：

https://stackoverflow.com/questions/47756675/how-to-do-expression-replacement-in-sage-as-in-mathematica