### sagemath fails to solve an equation and inequation

I do not understand why

```
var('R','p','x')
sol1=solve(R^(1/3)*p == x^(1/3),x)
show(sol1)
```

this work but this fails to isolate $x$

```
var('R','p','x')
sol1=solve(R^(1/3)*p <= x^(1/3),x)
show(sol1)
```

And that ~~this~~

```
var('R','p','x')
sol2=solve(0 == (R-x)^(1/3)*p + (1-p)* (-x)^(1/3),x)
show(sol2)
```

doesn't find $x$. And, as a consequence, of ~~course that ~~cours this :

```
var('R','p','x')
sol2=solve(0 <= (R-x)^(1/3)*p + (1-p)* (-x)^(1/3),x)
show(sol2)
```

fails. I have tried all simplification ways.