# Revision history [back]

Hi,

The ECL lib complains because (to its mind) the answer depends on the fact that y being positive negative or zero. To specify some restriction on variables within Sage just do

sage: var('y')
y
sage: assume(y > 0)
sage: solve((5*x-2)^(1/7)==y,x)
[x == 1/5*y^7 + 2/5]


Now, the operation x -> x^(1/7) looks unamiguous on RR because x -> x^7 is a bijection on RR.

An alternative would be to rewrite the equation

sage: var('y')
y
sage: assume(y > 0)
sage: solve((5*x-2)==y^7,x)
[x == 1/5*y^7 + 2/5]


Hi,

The ECL lib complains because (to its mind) the answer depends on the fact that y being positive negative or zero. To specify some restriction on variables within Sage just do

sage: var('y')
y
sage: assume(y > 0)
sage: solve((5*x-2)^(1/7)==y,x)
[x == 1/5*y^7 + 2/5]


Now, the operation x -> x^(1/7) looks unamiguous on RR because x -> x^7 is a bijection on RR.

An alternative would be to rewrite the equation

sage: var('y')
y
sage: assume(y > 0)
sage: solve((5*x-2)==y^7,x)
[x == 1/5*y^7 + 2/5]