Solve inequation not working with sqrt

Question

Diego Marvid 2020-9-28

回答： Prudhvi Peddagoni 2020-10-1

I tried to solve a simple inequation that had square root of the variable and the solve() function is not giving me the correct answer.

The inequation is:

The code is:

clear;
syms k real
eq = ( -1 + sqrt(1-4*k) )/2 < 1;
solve(eq, k)

And the answer is 0.

Since k is real the answer should be the interval (-2, 1/4)

Answer 1

Prudhvi Peddagoni 2020-10-1

Hi,

It seems that you did not enable ReturnConditions parameter. So the function is returning only one solution

solve(eq, k,'ReturnConditions',true);

This will return all the possible solutions. Please refer this link for more info.