Ask Your Question
0

Cannot solve equation with two radical terms

asked 2011-12-11 09:10:35 +0100

this post is marked as community wiki

This post is a wiki. Anyone with karma >750 is welcome to improve it.

I am learning Sage on the Notebook by reworking examples in my old algebra book (starting with page one). Could someone please explain the following behavior and how to solve the original equation?

This equation isn't getting solved:

solve(sqrt(2*x - 5) - sqrt(x - 3) == 1, x)

The output is:

[sqrt(x - 3) == sqrt(2*x - 5) - 1]

But the solution is x == 7 or x == 3

I tried the terms and they are solved:

solve(sqrt(2*x-5) == 1, x)
[x == 3]

solve(sqrt(x-3) == 1 , x)
[x == 4]

Thank you

edit retag flag offensive close merge delete

2 Answers

Sort by ยป oldest newest most voted
3

answered 2011-12-11 16:00:49 +0100

this post is marked as community wiki

This post is a wiki. Anyone with karma >750 is welcome to improve it.

Try using the to_poly_solve=True option. It's been on several people's wishlist to improve the documentation for the global solve function.

sage: solve(sqrt(2*x - 5) - sqrt(x - 3) == 1, x, to_poly_solve=True)
[x == 3, x == 7]

See also the answer to this older question:

http://ask.sagemath.org/question/397/...

edit flag offensive delete link more
0

answered 2011-12-11 09:21:40 +0100

this post is marked as community wiki

This post is a wiki. Anyone with karma >750 is welcome to improve it.

I saw a very similar question titled:

"strange behaviour when solving equations symbolically"

The answer basically was it can't do it.

I guess I have been so impressed by Sage so far, that I thought it looked like a simple problem.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Question Tools

Stats

Asked: 2011-12-11 09:10:35 +0100

Seen: 573 times

Last updated: Dec 11 '11