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Original Message (ID '80138') By Bill Simpson:
In Response To 'Re: Re: Undefined' --------- You have 24+25x+4 Sqrt[10] Sqrt[4-25y]-75y >0 && -24-25x+4 Sqrt[10] Sqrt[4-25y]+75y >0 && y < 4/25 and you want to substitute {x->1,y->2}. That gives In[1]:= 24+25x+4 Sqrt[10] Sqrt[4-25y]-75y/.{x->1,y->2} Out[1]= -101+(8*I)*Sqrt[115] In[2]:= -24-25x+4 Sqrt[10] Sqrt[4-25y]+75y/.{x->1,y->2} Out[2]= 101 + (8*I)*Sqrt[115] and you want to know whether each of those complex numbers is greater than zero, but there is no way to answer whether a complex is greater than or even less than zero. That is why you are getting the error message. What are you really trying to accomplish?