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Cannot solve equation with two radical terms

asked 13 years ago

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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

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answered 13 years ago

this post is marked as community wiki

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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/...

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answered 13 years ago

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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.

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Asked: 13 years ago

Seen: 601 times

Last updated: Dec 11 '11