Hi,

This one looks easy at first sight I think I'll just give you help, not sure for the solution.

(note that c is a real number since the RHS is a real number)

Square the equation :

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Recall that

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The equation is now :

Multiply both sides by (which is , otherwise, the first equation would be nonsense)

. The equation is now :

The discriminant is : , which isalwayspositive (because c is a real number).

Solutions are

We know that .

So find the range for c, such that both the solutions are in this interval :