Find all pairs of real numbers satisfying the following system:
Solution
Subtracting the given equations, we obtain , which is equivalent to
implying that either or .
In the latter case, is equivalent to
This is a quadratic equation in . Its discriminant is
which is a quadratic polynomial in – its discriminant in turn is , so the starting discriminant is for every real number , which implies that the equation does not have any real solution . Hence there are no solutions in this case.
In the remaining case, so both equations of a given system are reduced to , i.e. . This equation has three solutions , .
The only solutions are .
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