how to solve equation with square root

[CyberAngel]

(12-24-2019 07:30 AM)teerasak Wrote:  When using solve command to solve equation with square root, the calculator gives results including those negative value under square root. For example in the picture below.



solving equation Sqrt[x^2 + x -2] + Sqrt[x^2 + x -30] = Sqrt[2*x^2 + 2*x -32]

The calculator give result : -6, -2, 1,5, which is correct.

However, for some of them e.g -2, 1, when putting in x, it will give negative value under square root.

if we want the calculator to return only non-negative number under square root, what can we do?

It seems that when using CAS these solvers do not regard the CAS Settings flag
Complex: [ ]

You have to feed the answers back to the original equation yourself
to test if they give the Real domain answer.
:-(
Simply unbelievable, but real: fsolve may even give odd complex results.